The 50 most-cited articles in Inorganic Chemistry, 2020

A novel Co-based metal–organic framework (MOF) with the formula of {[Co 3 (BIBT) 3 (BTC) 2 (H 2 O) 2 ]·solvents} n ( JXUST-2, where JXUST denotes Jiangxi University of Science and Technology, BIBT = 4,7-bi(1 H -imidazol-1-yl)benzo-[2,1,3]thiadiazole, and H 3 BTC = 1,3,5-benzenetricarboxylic acid) has been solvothermally prepared, which takes 3D structure with a rare 3,4,6-c topology and contains intramolecular hydrogen bonds. Interestingly, the sensing investigations suggest that JXUST-2 could be considered as a multifunctional fluorescence sensor toward Fe 3+, Cr 3+, and Al 3+ via a turn-on effect with good reusability and detection limits of 0.13, 0.10, and 0.10 μM, respectively. The turn-on effect of JXUST-2 could be ascribed to an absorbance caused enhancement (ACE) mechanism. Notably, JXUST-2 is the first turn-on MOF fluorescent sensor for Fe 3+, Cr 3+, and Al 3+ simultaneously.

Developing highly stable materials for harmful ion detection in a water environment is of much importance and challenging. Here, two three-dimensional porous structures (termed as Eu-MOF and Tb-MOF) were successfully constructed by the strategy of anchoring Eu 3+ /Tb 3+ and rigid 1,2,4,5-benzenetetracarboxylic acid (H 4 BTEC) imidazole units (H 3 ICA) onto its frameworks. The obtained Eu-MOF and Tb-MOF display high water stability and fluorescence stability up to 30 days. Furthermore, luminescent studies reveal that Eu-MOF and Tb-MOF show rapid, recursive, and simultaneous sensing Fe 3+ and Cr 2 O 7 2– /CrO 4 2– ions in water. In addition, the sensing function possesses remarkable cyclicity and selectivity even with the existence of other analogous ions.

With the trigonal linker 4,4′,4″- s -triazine-2,4,6-triyltribenzoic acid as a building block, porous cobalt metal–organic frameworks (named as PCN) have been successfully prepared and directly utilized as active materials in alkaline battery-type devices. For comparison, their carbon-supported hybrids (CNFs/PCN) have also been employed as battery-type electrodes. We found that the pristine PCN displayed a better performance than the CNFs/PCN composite electrode in electrochemical cells. To further investigate their electrochemical performances, alkaline battery–supercapacitor hybrid (BSH) devices with these materials as positive electrodes and activated carbon (AC) as the negative electrode were fabricated. The results indicate that the PCN//AC BSH devices delivered a maximum energy density of 16.0 Wh kg –1 at a power density of 749 W kg –1 within the voltage range of 0–1.5 V, which are much higher than those of CNFs/PCN//AC devices (12.4 Wh kg –1 at 753 W kg –1 ).

In recent years, the demand for near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) has increased rapidly, leading to more and more attention being paid to the research of broad-band near-infrared phosphors. In this work, Cr 3+ -doped Ca 2 LuScGa 2 Ge 2 O 12 (CLSGG:Cr 3+ ) phosphors with broad-band NIR emission were prepared through traditional high-temperature solid-state reactions. The crystal structures of the phosphors were analyzed by X-ray diffraction (XRD) and Rietveld refinement. The photoluminescence excitation (PLE) spectra of the synthesized CLSGG:Cr 3+ phosphors exhibit a strong absorption band in the 400–500 nm region, which matches well with a blue-light-emitting chip. The photoluminescence (PL) spectra of the phosphors show broad-band emission ranging from 650 to 1100 nm with a full width at half-maximum (fwhm) of about 150 nm. At 423 K, the integrated emission intensity of CLSGG:0.02Cr 3+ is about 59% of that at room temperature. A NIR pc-LED device was fabricated by combining a mixture of as-synthesized CLSGG:0.02Cr 3+ phosphor and silicone with a…

Abstract Intrinsic properties of a compound (e.g., electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior. In the case of nanomaterials, these fundamental properties depend on the occurrence of quantum mechanical size effects and on the considerable increase of the surface to bulk ratio. Here, we explore the size dependence of both crystal and electronic properties of CeO2 nanoparticles (NPs) with different sizes by state-of-the art spectroscopic techniques. X-ray diffraction, X-ray photoelectron spectroscopy, and high-energy resolution fluorescence-detection hard X-ray absorption near-edge structure (HERFD-XANES) spectroscopy demonstrate that the as-synthesized NPs crystallize in the fluorite structure and they are predominantly composed of CeIV ions. The strong dependence of the lattice parameter with the NPs size was attributed to the presence of adsorbed species at the NPs surface thanks to Fourier transform infrared spectroscopy and thermogravimetric analysis measurements. In addition, the size…

Colorimetric assays have drawn increasing research interest with respect to the quantitative detection of hydrogen peroxide (H 2 O 2 ) based on artificial enzymes because of their advantages with respect to natural enzymes, including design flexibility, low cost, and high stability. Regardless, the majority of the artificial enzymes exhibit low affinity to H 2 O 2 with large Michaelis–Menten constants ( K m ). This indicates that the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to blue-colored oxTMB requires a high H 2 O 2 concentration, hindering the sensitivity of the colorimetric assay. To address this problem, novel reduced Co 3 O 4 nanoparticles (R-Co 3 O 4 ) have been synthesized in this study via a step-by-step procedure using ZIF-67 as the precursor. R-Co 3 O 4 exhibits a considerably enhanced peroxidase-like activity when compared with that exhibited by pristine Co 3 O 4 (P-Co 3 O 4 ). The catalytic process in the case of R-Co 3 O 4 occurs in accordance with the typical Michaelis–Menten equation, and the affinity of R-Co 3 O 4 to H 2 O 2 is apparently higher…

Hydrogen evolution from water splitting by means of a photocatalytic approach is an ideal future energy source and free of fossil reserves, in contrary photocatalytic O 2 evolution remains a bottleneck due to high over potential and low efficiency. For reasonable use of solar light, photocatalysts must be sufficiently stable and efficient toward harvesting of sunlight from both theoretical and practical viewpoints. In this regard, here we have prepared MoS 2 -modified UiO-66-NH 2 MOF through a facile hydrothermal technique and evaluated its efficiency toward photocatalytic H 2 and O 2 evolution by water splitting in the presence of sacrificial agents. A couple of similar type of analyses have been studied previously; however, this analysis represents a diverse scientific approach on the basis of interfacial contact toward reveal the actual potential of nanoflakes MoS 2 as well as UiO-66-NH 2 . In this regard the as-synthesized photocatalyst was well-characterized by XRD, FTIR, UV–vis diffuse reflectance spectra, FESEM, HRTEM, XPS, and BET analysis techniques, which provide…

There is a challenge for noncontact temperature-sensing techniques and the related materials, in which a highly reliable contactless thermometer probe with low cost and high sensitivity is in demand. Here, the Lu 3 Al 5 O 12:Ce 3+ /Mn 4+ phosphor has been designed and prepared for the high-performance fluorescence temperature-sensing application in a novel one-pot, self-redox, solid-state process. Benefiting from the different electron–lattice/phonon interactions of Ce 3+ and Mn 4+, two distinguishable emission peaks with significantly different temperature responses originating from Ce 3+ and Mn 4+ are realized. Applying the fluorescence intensity ratio of Mn 4+ versus Ce 3+ and the decay lifetime of Mn 4+ emission as the temperature readout, a dual-mode optical temperature-sensing mechanism was proposed and studied in the temperature range of 100–350 K. The maximum relative sensitivities ( S r ) are derived as 4.37 and 3.22% K –1 respectively, as well as a large chromaticity shift visible to naked eyes (Δ E = 153 × 10 –3 in 100–350 K) is observed. This is the first report of a Ce…

In this work, for the first time, we fabricated a novel covalent organic framework (COF)-based 2D–2D heterojunction composite MoS 2 /COF by a facile hydrothermal method. The results of photocatalytic degradation of TC and RhB under simulated solar light irradiation showed that the as-prepared composite exhibited outstanding catalytic efficiency compared with pristine COFs and MoS 2 . The significantly enhanced catalytic efficiency can be ascribed to the formation of 2D–2D heterojunction with a well-matched band position between COF and MoS 2, which can effectively restrain the recombination of charge carriers and increase the light absorption as well as the specific surface area. Moreover, the fabricated 2D–2D layered structure can effectively increase the contact area with an intimate interface contact, which greatly facilitates the charge mobility and transfer in the interfaces. This study reveals that artful integration of organic (COFs) and inorganic materials into a single hybrid with a 2D–2D interface is an effective strategy to fabricate highly efficient photocatalysts.

Two-dimensional (2D) Co-based MOF-on-MOF heterojunction nanostructures with improved electrocatalytic activity were successfully constructed via a mild two-step solution route, employing Co 2+ ions as the center atoms, and 1,4-benzenedicarboxylate (BDC) and 4,4′-biphenyldicarboxylate (BPDC) as ligands. The as-obtained heterojunction nanostructures were characterized by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) technologies. Electrochemical measurements showed that as-prepared Co-BPDC/Co-BDC heterojunction nanostructures presented markedly enhanced OER electrocatalytic activity, compared with single Co-BPDC, Co-BDC, and/or their physical mixture. Also, the Co-BPDC/Co-BDC-3 heterojunction prepared after treatment for 3 h exhibited the strongest catalytic activity. To reach the current density j geo = 10 mA cm –2, the Co-BPDC/Co-BDC-3 heterojunction-modified glassy carbon…

Commercial white LED devices usually suffer from a high color temperature and poor color rendering. Developing a new, efficient, and stable red phosphor is the key to solving this problem. In this work, a series of pure Ca 3 Y 2-x B 4 O 12: x Eu 3+ (0 < x ≤ 2) samples, including the new and fully transitional borate phosphor Ca 3 Eu 2 B 4 O 12 (CEBO), have been successfully prepared by solid-state reaction synthesis. CEBO is isostructural with Ca 3 Y 2 B 4 O 12 (CYBO), belonging to the orthorhombic system with space group Pnma (No. 62). Under optimal 393 nm excitation, this borate exhibits a strong red emission, peaking at 615 nm, with high color purity. Interestingly, the luminescence of CEBO is relatively higher than that of CYBO:Eu 3+ phosphors. The quantum yield of this non-concentration-quenching phosphor reaches 95.6%. Furthermore, a warm pc-WLED device has been fabricated by mixing as-prepared CEBO powders and commercial BaMgAl 10 O 17:Eu 2+ and (Sr, Ba) 2 SiO 4:Eu 2+ phosphors, which exhibits a high color rendering index (Ra = 83.7) along with a color temperature of around…

The purpose of this study was the investigation of the potential of MIL-101(Fe) for load and sustained release of curcumin (CCM), as an anticancer drug, with pH stimulus. The reasons for choosing this type of metal-organic framework (MOF) are its high surface area, acceptable stability in a water medium, and its biocompatible components (iron and terephthalic acid) with low toxicity to normal cells. The obtained results from UV-vis analysis confirmed that this MOF is a smart carrier with a higher release rate in acidic pH (pH 5), which is a condition similar to that in cancer cells, than that at pH 7.4 (in normal cells). Therefore, this MOF is a pH-stimulus-controlled release carrier with 56.3% drug loading content and sustained drug release over 22 days. In order to evaluate the cell viability after treatment with free CCM, MIL-101(Fe), and MIL-101(Fe)@CCM, the cytotoxicity investigation using MTT assays was performed against HeLa and HEK 293 cell lines up to 48 h. Obtained results showed that MIL-101(Fe)@CCM exhibited more cell growth inhibition effect on HeLa cells in comparison…

Lanmodulin (LanM) is a recently discovered protein that undergoes a large conformational change in response to rare-earth elements (REEs). Here, we use multiple physicochemical methods to demonstrate that LanM is the most selective macromolecule for REEs characterized to date and even outperforms many synthetic chelators. Moreover, LanM exhibits metal-binding properties and structural stability unseen in most other metalloproteins. LanM retains REE binding down to pH ≈ 2.5, and LanM-REE complexes withstand high temperature (up to 95 °C), repeated acid treatments, and up to molar amounts of competing non-REE metal ions (including Mg, Ca, Zn, and Cu), allowing the protein's use in harsh chemical processes. LanM's unrivaled properties were applied to metal extraction from two distinct REE-containing industrial feedstocks covering a broad range of REE and non-REE concentrations, namely, precombustion coal and electronic waste leachates. After only a single all-aqueous step, quantitative and selective recovery of the REEs from all non-REEs initially present (Li, Na, Mg, Ca, Sr, Al, Si,…

Abstract Sensing and monitoring toxic contaminants like Fe3+, CrO42–, and Cr2O72– ions in water is very important due to their harmful effects on biological and environmental systems. Enhanced hydrolytic stability, sensitivity, and selectivity, in addition to their excellent luminescence properties, are important attributes of metal–organic framework (MOF)-based sensors for sensing applications. In this work, the water stable Zn–MOF [Zn2(tpeb)­(bpdc)2] (where tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene and bpdc = biphenyl-4,4′-dicarboxylic acid) was synthesized and characterized. The framework retains its crystallinity and structural integrity in harsh acidic and basic conditions (pH 4–11). Most interestingly, the Zn–MOF demonstrates a strong blue luminescence in water that can be quenched selectively only by contaminants like Fe3+, CrO42–, and Cr2O72– ions. Higher Ksv values and low detection limits in selective luminescence quenching confirm the superior sensing performance, which is comparable to those of contemporary materials. Furthermore, in all cases, quenching efficiency…

Two novel thorium-based metal–organic frameworks (MOFs), namely Th-SINAP-7 and Th-SINAP-8, have been synthesized via the solvothermal reactions of thorium nitrate and 1,4- or 2,6-naphthalenedicarboxylic acid in the presence of acid modulators. Bearing the rigid aromatic architectures, Th-SINAP-7 and Th-SINAP-8 exhibit exceptional chemical (from pH 1 to 12) and thermal stabilities (up to 520 °C), as well as ionizing radioresistance (2 × 10 5 Gy β and γ irradiations). The highly porous nature and conjugated π-electrons of naphthalene on the organic linkers endow high affinity of both MOFs toward I 2 molecules owning to the charge transfer between π-electrons of the host networks and the guest iodine molecules, as evidenced by combined techniques including of FTIR, PXRD, SEM-EDS, UV–vis spectroscopy, XPS, and Raman spectroscopy. Particularly, Th-SINAP-8 can efficiently remove >99% I 2 from cyclohexane solution and exhibit guest uptake of iodine vapor with an adsorption capacity of 473 mg/g.

Cluster-based coordination polymers (CCPs) have shown promise as capacitors. To investigate the relativity between capacitor performance and crystal structure, herein, five new CCPs based on organophosphorus Strandberg-type clusters were synthesized via in situ hydrothermal reactions at different pH’s, namely, (H 2 bipy) 2 [(C 6 H 5 PO 3 ) 2 Mo 5 O 15 ]·2H 2 O ( 1 ), (H 2 bipy) 1.5 [Cu I (bipy)(C 6 H 5 PO 3 ) 2 Mo 5 O 15 ]·H 2 O ( 2 ), H 2 [Cu I 2 (bipy) 2.5 (C 6 H 5 PO 3 ) 2 Mo 5 O 15 ]·2H 2 O ( 3 ), Na 2 [Cu I 4 Cu II (bipy) 4 (C 6 H 5 PO 3 ) 2 (Mo 5 O 15 ) 2 ]·15H 2 O ( 4 ), [Cu II 2 (bipy)(H 2 O) 4 (C 6 H 5 PO 3 ) 2 Mo 5 O 15 ] ( 5 ) (bipy = 4,4′-bipyridine). Compound 1 is a zero-dimensional monomer, in which the protonated bipy ligands as countercations combine Strandberg-type clusters by hydrogen bonding and π–π interaction forming a supramolecular layer. Compound 2 represents a unique one-dimensional (1D) channel chain structure linked by intermolecular hydrogen bonding and π–π interaction. Compounds 3 and 4 exhibit the first example of an interdigitated architecture based on…

The composition-tuned, structure-modified, and morphology-controlled nanoscale metal–organic frameworks (MOFs) are quite important to improve the electrochemical performances for supercapacitors. In this work, a solvent-controlled method to prepare amino-functionalized bimetal MOFs with various morphologies is proposed. Three different morphologies of NiCo-MOFs, such as nanospheres, nanosheet-assembled hollow spheres (NSHSs), and rhombus sheets, have been successfully synthesized by using different solvents. The as-prepared three nanoscale NiCo-MOFs are comparatively characterized and are endowed a possible mechanism on nucleation and crystal growth controlling morphology. When used as electrode materials for supercapacitors, all NiCo-MOFs have excellent electrochemical properties. Specifically, the NiCo-MOF NSHS owns the best specific capacitance, which can achieve 1126.7 F g –1 at the current density of 0.5 A g –1 and maintain 93% of its original capacitance at the current density of 10 A g –1 after 3000 charge–discharge cycles. Moreover, an asymmetric supercapacitor device…

Contrast-enhanced magnetic resonance imaging (MRI) is an indispensable tool for diagnostic medicine. However, safety concerns related to gadolinium in commercial MRI contrast agents have emerged in recent years. For patients suffering from severe renal impairment, there is an important unmet medical need to perform contrast-enhanced MRI without gadolinium. There are also concerns over the long-term effects of retained gadolinium within the general patient population. Demand for gadolinium-free MRI contrast agents is driving a new wave of inorganic chemistry innovation as researchers explore paramagnetic transition-metal complexes as potential alternatives. Furthermore, advances in personalized care making use of molecular-level information have motivated inorganic chemists to develop MRI contrast agents that can detect pathologic changes at the molecular level. Recent studies have highlighted how reaction-based modulation of transition-metal paramagnetism offers a highly effective mechanism to achieve MRI contrast enhancement that is specific to biochemical processes. This Viewpoint…

Lanthanide (such as Tb and Eu) metal–organic frameworks (MOFs) have been widely used in fluorescent probes because of their multiple coordination modes and brilliant fluorescence characteristic. Many lanthanide MOFs were applied in detecting metal ions, inorganic anions, and small molecules. However, it’s rarely reported that Ln-MOF was devoted to detecting malachite green (MG) and uric acid (UA). We prepared a europium-based metal–organic framework (Eu-TDA) (TDA = 2,5-thiophenedicarboxylic acid group). Luminescence studies demonstrated that Eu-TDA can rapidly detect MG and UA with excellent selectivity and sensitivity, where individual quenching efficiency K sv (MG: 5.8 × 10 5 M –1; UA: 4.15 × 10 4 M –1 ) and detection limit (MG: 0.0221 μM; UA: 0.689 μM) were regarded as the excellent MOF sensors for detecting MG and UA. The quenching of Eu-TDA’s fluorescence emission by MG and UA was likely due to the spectral overlap, energy transfer, and competition. Among 11 metal cations and 14 anions, Eu-TDA can quickly and effectively recognize MG and UA with highly selective and sensitive…

In light of the chemical exploitation of CO 2, new reusable materials for efficiently catalyzing the cycloaddition of CO 2 and epoxides under moderate conditions are needed. Herein, a new series of isostructural metal–organic frameworks (MOFs) M 2 (EDOB) [EDOB 4– = 4,4′-(ethyne-1,2-diyl)bis(2-oxidobenzoate), M = Mg, Ni, Co, Zn, Cu, Fe], known as M-MOF-184, analogous to a well-studied MOF-74 structure, were synthesized and fully characterized. The M-MOF-184 (M = Mg, Co, Ni, Zn) frameworks exhibit accessible mesopore channels (24 Å) and high porosity. Among them, Mg-MOF-184 demonstrated the most upper surface area (>4000 m 2 g –1 ) in any reported MOF-74-type frameworks. Furthermore, Co-MOF-184 revealed the highest CO 2 uptake (73 cm 3 g –1, at 298 K), and Zn-MOF-184 showed the highest catalytic activity upon the cycloaddition of CO 2 (96% conversion, 86% selectivity, and 82% yield) under mild conditions (1 atm CO 2, 80 °C, 6 h, and solvent-free). Notably, the catalytic performance of Zn-MOF-184 outperformed that of the original M-MOF-74 (M = Mg, Co, Zn) materials and various Zn-based…

For better exciton separation and high catalytic activity, the most trailblazing stratagem is to construct defect engineered low-dimensional p–n heterojunction framed photocatalytic systems. In this context, we have developed a rod–sheet (1D–2D) p–n heterojunction of MCeO 2 –BiFeO 3 by a simple hydrothermal method and scrutinized its photocatalytic performance toward N 2 fixation and phenol/Cr(VI) detoxification. The intimate contact between MCeO 2 and BiFeO 3 in the junction material is well established via X-ray diffraction (XRD), UV–vis diffuse reflectance spectrosopy (DRS), transmission electron microscopy (TEM), and photoelectrochemical studies. Further, scanning electron microscopy (SEM) and TEM pictures clearly support the decoration of MCeO 2 nanorods over BiFeO 3 sheets and also depict the junction boundary. Additionally, photoluminescence (PL), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and Raman measurements give solid evidence toward the presence of an oxygen vacancy. Moreover, the Mott–Schottky result indicates a feasible band edge…

Abstract A number of high-entropy alloys (HEAs) in the TiVZrNbHf system have been synthesized by arc melting and systematically evaluated for their hydrogen sorption characteristics. A total of 21 alloys with varying elemental compositions were investigated, and 17 of them form body-centered-cubic (bcc) solid solutions in the as-cast state. A total of 15 alloys form either face-centered-cubic (fcc) or body-centered-tetragonal (bct) hydrides after exposure to gaseous hydrogen with hydrogen per metal ratios (H/M) as high as 2.0. Linear trends are observed between the volumetric expansion per metal atom [(V/Z)fcc/bct – (V/Z)bcc/hcp]/(V/Z)bcc/hcp with the valence electron concentration and average Pauling electronegativity (χp) of the alloys. However, no correlation was observed between the atomic size mismatch, δ, and any investigated hydrogen sorption property such as the maximum storage capacity or onset temperature for hydrogen release.

Abstract Metal complexes have numerous applications in the current era, particularly in the field of pharmaceutical chemistry and catalysis. A novel synthetic approach for the same is always a beneficial addition to the literature. Henceforth, for the first time, we report the formation of three new Pd­(II) complexes through the Michael addition pathway. Three chromone-based thiosemicarbazone ligands (SVSL1–SVSL3) and Pd­(II) complexes (1–3) were synthesized and characterized by analytical and spectroscopic tools. The Michael addition pathway for the formation of complexes was confirmed by spectroscopic studies. Distorted square planar structure of complex 2 was confirmed by single-crystal X-ray diffraction. Complexes 1–3 were subjected to DNA- and BSA-binding studies. The complex with cyclohexyl substituent on the terminal N of thiosemicarbazone (3) showed the highest binding efficacy toward these biomolecules, which was further understood through molecular docking studies. The anticancer potential of these complexes was studied preliminarily by using MTT assay in cancer and normal…

The fabrication of highly efficient and sustainable electrocatalysts used for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is exceedingly challenging and warranted for overall water splitting. In this work, we successfully synthesized a series of metal–organic frameworks (MOFs), namely, as Fe 2 M-MOF (M = Fe, Co, Ni, Zn, Mn; H 4 L = 3,3,5,5′-azoxybenzenetetracarboxylic acid) under a simple and mild condition, in which the Fe 3 cluster as a basic building unit was replaced by the second kind of metal center; at the same time, a redox-active organic linker was adopted. The Fe 2 M-MOF system as a multifunctional catalyst realizes great improvement of the OER and HER performances. Among of them, the Fe 2 Co-MOF catalyst exhibits an extremely low overpotential of 339 mV at a current density of 10 mA cm –2 and a very small Tafel slope of 36.2 mV dec –1 in an alkaline electrolyte for OER. This result has far exceeded the commercial catalyst IrO 2 . Meanwhile, Fe 2 Zn-MOF manifests excellent HER activity with a small overpotential of 221 mV at 10 mA cm –2 and a low…

In this paper, BaY 2 O 4:Yb 3+ /Er 3+, a high efficient red upconversion (UC) material, is first utilized as an optical thermometer in the biological window, accomplished through the fluorescence intensity ratio (FIR) of thermally coupled Stark sublevels of 4 F 9/2 (FIR (654/663) ). The maximum absolute sensitivity of FIR (654/663) ) is 0.19% K –1 at 298 K, which is much higher than most previous reports about FIR-based temperature sensors located in the biological windows. More importantly, the groove of FIR (654/663) for thermometry is nicely located in the physiological temperature range, indicating its potential thermometry application value in biomedicine. Furthermore, a simply ex vivo experiment is implemented to evaluate the penetration depth of the red emission in biological tissues, revealing that a detection depth of 6 mm can be achieved without any effect on the FIR values of I 654 to I 663 . Beyond that, the temperature sensing behaviors of the thermally coupled levels 2 H 11/2 and 4 S 3/2 (FIR (523/550) ) are also investigated in detail. In the studied temperature…

By using the reduced Schiff base tricarboxylate ligand H 3 cip, one novel 3D Cd-based coordination polymer ( Cd-CP ) with the formula [Cd(Hcip)(bpea) 0.5 (H 2 O)] n (H 3 cip = 5-(3-carboxybenzylamino)isophthalic acid, bpea = 1,2-bis(4-pyridyl)ethane) has been solvothermally synthesized. The prepared Cd-CP possesses a 4-connected CdSO 4 net based on dinuclear {Cd 2 } units. Luminescence measurements revealed that the complex exhibited ratiometric turn-on luminescence responses toward Al 3+ and Cr 3+ with a significant color change, which could be easily distinguished by the naked eye under ultraviolet light. Cd-CP can also respond to Fe 3+ through a turn-off mechanism. Interestingly, the luminescence quenched by Fe 3+ @ Cd-CP can be recovered and increased significantly by adding some competitive Al 3+, while Cr 3+ can only marginally increase the luminescence intensity of Fe 3+ @ Cd-CP . Moreover, the detection of the three aforementioned metal ions can be realized by using Cd-CP -coated test papers, extending the potential application regions of the reported material to…

The lithium-argyrodites Li6PS5X (X = Cl, Br, I) exhibit high lithium-ion conductivities, making them promising candidates for use in solid-state batteries. These solid electrolytes can show considerable substitutional X−/S2− anion-disorder, with greater disorder typically correlated with higher lithium-ion conductivities. The atomic-scale effects of this anion site-disorder within the host lattice—in particular how lattice disorder modulates the lithium substructure—are not well understood. Here, we characterize the lithium substructure in Li6PS5X (X = Cl, Br, I) as a function of temperature and anion site-disorder, using Rietveld refinements against temperature-dependent neutron diffraction data. Analysis of these high-resolution diffraction data reveals an additional lithium position previously unreported for Li6PS5Xargyrodites, suggesting that the lithium conduction pathway in these materials differs from the most common model proposed in earlier studies. Analysis of the Li+ positions and their radial distributions reveals that greater inhomogeneityof the local anionic charge,…

The complete removal of tetracycline residuals under visible light still is a challenging task because of their robust ring structure. To tackle this issue, we explore a novel Bi 2 O 3 -sensitized TiO 2 visible-light photocatalyst by combining p–n heterojunction with hollow structure. The hollow TiO 2 /Bi 2 O 3 photocatalyst manifests excellent photocatalytic performance and recyclability toward the complete degradation (100%) of antibiotics under visible light (λ > 420 nm) because of the synergistic effect of p–n heterojunction and hollow structure, successfully overcoming the challenge of the incomplete removal of antibiotics over almost all of the reported visible-light photocatalysts. Additionally, the effects of inorganic ions, pH value, water matrix, and outdoor light on the degradation of tetracyclines were investigated with many details. Notably, the degradation pathways and mechanism of tetracycline were revealed according to trapping experiments, HPLC-MS, and photoelectrochemical characterizations. Therefore, this work provides a new insight into developing visible-light…

Transition-metal sulfide is a good kind of material for supercapacitors because of the large capacity. Nevertheless, the low electroconductivity, slow reaction kinetics, and limited active centers lead to poor electrochemical properties such as long-term cycling stability. In the present work, nano nickel metal–organic framework (Ni-MOF) was constructed by using the nitrogen-rich functional group ligand 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazin and compounded with carbon nanotubes (CNTs) to prepare Ni-MOF/CNTs composite, which was used as a precursor to prepare the MOFs-derived NC/Ni–Ni 3 S 4 /CNTs composite with the Ni 3 S 4 uniformly distributed in the three-dimensional (3D) conductive network. The rich nitrogen doping and 3D conductive network constructed by CNTs improved the conductivity, prompted the rapid entry of electrolyte, and improved the reaction kinetics of NC/Ni–Ni 3 S 4 /CNTs, thus obtained excellent specific capacitance, coulomb efficiency, and cyclic stability. The specific capacitance of NC/Ni–Ni 3 S 4 /CNTs is 1489.9 F/g at 1 A/g, which remains 800 F/g…

K-fluorescence X-ray emission spectroscopy (XES) is receiving growing interest in all fields of natural sciences to investigate the local spin. The spin sensitivity in Kβ (Kα) XES stems from the exchange interaction between the unpaired 3p (2p) and the 3d electrons, which is greater for Kβ than for Kα. We present a thorough investigation of a large number of iron-bearing compounds. The experimental spectra were analyzed in terms of commonly used quantitative parameters (Kβ 1,3 -first moment, Kα 1 -full width at half-maximum, and integrated absolute difference −IAD−), and we carefully examined the difference spectra. Multiplet calculations were also performed to elucidate the underlying mechanisms that lead to the chemical sensitivity. Our results confirm a strong influence of covalency on both Kβ and Kα lines. We establish a reliable spin sensitivity of Kβ XES as it is dominated by the exchange interaction, whose variations can be quantified by either Kβ 1,3 -first moment or Kβ-IAD and result in a systematic difference signal line shape. We find an exception in the Kβ XES of Fe 3+…

Organic–inorganic hybrid metal halides with broad-band emission are currently receiving an increasing interest for their unique light emission properties. Here we report a novel lead-free zero-dimensional (0D) tin halide, (C 8 H 14 N 2 ) 2 SnBr 6, in which isolated [SnBr 6 ] 4– octahedrons are cocrystallized with organic cations, 1,3-bis(aminomethyl)benzene (C 8 H 14 N 2 2+ ). Upon photoexcitation, the bulk crystals exhibit broad-band green emission peaking at 507 nm with a full width at half-maximum (fwhm) of 82 nm (0.395 eV), a Stokes shift of 157 nm (1.09 eV), and a photoluminescence quantum yield (PLQY) of 36 ± 4%. Combined structural analysis and density functional theory (DFT) calculations indicate that the excited state structural distortion of [SnBr 6 ] 4– octahedral units account for the formation of this green emission. The relatively small Stokes shift and narrow fwhm of the emission are hence caused by the reduced distortion of [SnBr 6 ] 4– octahedrons and rigid molecular structure. The discovery of lead-free (C 8 H 14 N 2 ) 2 SnBr 6 and insight into the mechanism of…

Metal–organic frameworks (MOFs) show a distinctive pre-eminence over other heterogeneous systems for adsorption of carbon dioxide (CO 2 ) gas and fluorescence detection of water contaminating ions, where integration of both these attributes along with enhancement of pore functionality and water stability is crucial for potential applications related to environmental remediation. Pore functionalization has been achieved in a 2-fold interpenetrated, mixed-ligand Cd(II)-framework [Cd 1.5 ( L ) 2 ( bpy )(NO 3 )]·2DMF·2H 2 O ( CSMCRI-5 ) (H L = 4-(4-carboxyphenyl)-1,2,4-triazole, bpy = 4,4′-bipyridine, DMF = dimethylformamide, CSMCRI = Central Salt & Marine Chemicals Research Institute) by utilizing a bifunctional ligand H L . The bpy -pillared framework, containing diverse Cd(II) nodes, optimum sized voids, and free N-atom affixed one-dimensional porous channels, shows notable structural robustness in diverse organic solvents and water. In spite of a negligible surface area, the activated MOF ( 5a ) exhibits good CO 2 uptake and highly selective CO 2 adsorption over N 2 (259.94) and CH…

Abstract Here, we present the synthesis and crystal structure of Rb3InCl6 prepared from air stable reagents via a two-step process that proceeds through the intermediate Rb2InCl5·H2O. Rb3InCl6 crystallizes with the Rb3YCl6 structure type (C2/c), which can be derived from the double perovskite structure by noncooperative tilting of isolated [InCl6]3– octahedra. Despite this lowering of symmetry, the optical properties are similar to the cubic double perovskite Cs2NaInCl6. Partial substitution of In3+ with Sb3+ in Rb3InCl6 results in intense cyan-green photoluminescence originating from localized 5s2 to 5s15p1 electronic transitions of [SbCl6]3– polyatomic anions. In comparison with the cubic double perovskite phosphor Cs2NaInCl6:Sb3+, the octahedral tilting distortion increases the electronic isolation of the In/Sb-centered octahedra thus facilitating electron and hole localization on Sb3+ sites, leading to bright photoluminescence. The distorted crystal structure also leads to a larger Stokes shift (1.29 eV) and a corresponding red shift of the emission peak (λmax = 522 nm) compared…

Abstract As increasing demand for noncontact temperature sensing, the development of a high-performance optical thermometer probe is more and more urgent. In this work, an efficient dual-mode optical thermometry strategy based on the Pr3+/Dy3+ energy transfer (ET) in some typical double-perovskite oxides is presented, which offers a promising way to design FIR/lifetime dual-mode optical thermometry with excellent temperature-measuring sensitivity and signal discrimination. According to this strategy, double-perovskite La2MgTiO6:Pr3+/Dy3+ phosphors are successfully synthesized. On the basis of diverse thermal responses between Pr3+ and Dy3+, the FIR of Pr3+ to Dy3+ (four FIR mode) in this material displays outstanding optical thermometry performance from 298 to 548 K. The maximum absolute and relative sensitivities (Sa and Sr) of mode 1 are 0.09 and 2.357% K–1, being better than the current optical temperature measurement materials. For the fluorescence lifetime mode, the Sa‑max and Sr‑max values reach 2.85 × s 10–4 and 1.814% K–1. Furthermore, the dual-mode optical thermometry…

Both imidazol-2-ylidene (ImNHC) and 1,2,3-triazol-5-ylidene (tzNHC) have evolved to be elite groups of N-heterocyclic carbene (NHC) ligands for homogeneous catalysis. To develop efficient ruthenium(II)-based catalysts incorporating these ligands for C–N bond-forming reactions via hydrogen-borrowing methodology, we utilized chelating ligands integrated with ImNHC and mesoionic tzNHC donors connected via a CH 2 spacer with a diverse triazole backbone. The synthesized ruthenium(II) complexes 3 are found to be highly efficient for C–N bond formation across a wide range of primary amine and alcohol substrates under solvent-free conditions, and among all of the complexes studied here, catalyst 3a with a mesityl substituent displayed maximum activity. To our delight, catalyst 3a is also effective for the selective mono-N-methylation of various anilines utilizing methanol as a coupling partner, known to be relatively more difficult than other alcohols. Furthermore, complex 3a also delivers various substituted quinolines successfully via the reaction of 2-aminobenzyl alcohol with several…

We report a one-step, solvent-free, green approach for the mechanochemical stabilization of hybrid organic–inorganic lead halide (MAPbBr 3 ) perovskite quantum dots (PQDs) within perovskite metal–organic frameworks (MOFs) [MA-M(HCOO) 3 ] [M = Mn and Co; MA = methylammonium (CH 3 NH 3 + )]. The perovskite MOF acts as a template and source of MA cations for growing and stabilizing hybrid PQDs. The synthesis of the composite has been carried out mechanochemically, without the use of any external reagents by simply grinding the perovskite MOF with PbBr 2 . MAPbBr 3 @MA-Mn(HCOO) 3 composite shows high chemical stability in several solvents. Its excellent processability has been demonstrated by using it as an electrode material which shows photoelectrochemical activity in the presence of light.

Multivariate metal–organic frameworks (MTV-MOFs) have drawn much attention in recent years for their promising applications in many fields of chemistry and materials. Constructing functional MOFs from multiple components for electrochemical water is crucial to high performance renewable energy storage and conversion devices. In this work, a series of bitmetallic-, trimetallic-, and tetrametallic-MOF-74/NFs were grown in situ on nickel foam (NF) by a facile solvothermal route. Specifically, the optimized FeCoMnNi-MOF-74/NF with a multilevel and hollow nanostructure was successfully fabricated and used as highly efficient bifunctional electrocatalysts for water splitting. It exhibited an ultralow overpotential of 250 and 108 mV to achieve the current density of 50 and 10 mA cm –2, along with the relatively small Tafel slope of 41.28 and 72.89 mV dec –1 for OER and HER in 1 M KOH, respectively. It is superior to other multimetallic-MOF-74 composites at the same condition and also surpasses the benchmark of commercial noble-metal catalysts as well. As a result, a low cell voltage of ca.…

Abstract The interpretation of in vitro cytotoxicity data of Cu­(II)-1,10-phenanthroline (phen) complexes normally does not take into account the speciation that complexes undergo in cell incubation media and its implications in cellular uptake and mechanisms of action. We synthesize and test the activity of several distinct Cu­(II)-phen compounds; up to 24 h of incubation, the cytotoxic activity differs for the Cu complexes and the corresponding free ligands, but for longer incubation times (e.g., 72 h), all compounds display similar activity. Combining the use of several spectroscopic, spectrometric, and electrochemical techniques, the speciation of Cu-phen compounds in cell incubation media is evaluated, indicating that the originally added complex almost totally decomposed and that Cu­(II) and phen are mainly bound to bovine serum albumin. Several methods are used to disclose relationships between structure, activity, speciation in incubation media, cellular uptake, distribution of Cu in cells, and cytotoxicity. Contrary to what is reported in most studies, we conclude that…

In this work, a novel zirconium-based metal–organic framework (MOF) composite material, UiO-(OH) 2 @RhB, has been solvothermally prepared with zirconyl chloride octahydrate, 2,5-dihydroxyterephthalic acid, and rhodamine B (RhB) for ratiometric fluorescence sensing of Al 3+ ions in an aqueous medium. The luminescence measurement results showed that, at the single excitation wavelength of 420 nm, the fluorescence intensity of the ligand at 500 nm increased significantly in the case of Al 3+, while that of RhB at 583 nm changed slightly, together with an apparent color change. Under optimal conditions, UiO-(OH) 2 @RhB exhibited an extraordinary sensitivity (10 nM), good selectivity, and a fast response (2 min) for Al 3+ . As far as we know, the limit of detection is superior to that of the current reported MOF-based Al 3+ fluorescence sensors. The response mechanism suggested that −OH could capture Al 3+ in water through coordination and high electrostatic affinity and achieved turn-on ratiometric fluorescence through the excited-state intramolecular proton transfer process and stable…

Abstract The separation of adjacent lanthanides continues to be a challenge worldwide because of the similar physical and chemical properties of these elements and a necessity to advance the use of clean-energy applications. Herein, a systematic structure–performance relationship approach toward understanding the effect of N-alkyl group characteristics in diglycolamides (DGAs) on the separation of lanthanides­(III) from a hydrochloric acid medium is presented. In addition to the three most extensively studied DGA complexants [N,N,N′,N′-tetra­(n-octyl)­diglycolamide, TODGA; N,N,N′,N′-tetra­(2-ethylhexyl)­diglycolamide, TEHDGA; N,N′-dimethyl-N,N′-di­(n-octyl)­diglycolamide, DMDODGA], 12 new extracting agents with varying substitution patterns were designed to study the interplay of steric and electronic effects that control rare-earth element extraction. Subtle changes in the structure around diglycolamide carbonyl oxygen atoms result in dramatic shifts in the lanthanide extraction strength and selectivity. The effects of the chain length and branching position of N-alkyl substituents…

We first design and synthesize a dendritic aromatic 6-carboxyl linker (H 6 TDCPB), which is successfully assembled with Cd(II) ion to construct a porous metal–organic framework with a raw Cd 6 cluster, {[Cd 3 (TDCPB)·2DMAc]·DMAc·4H 2 O} n (namely, complex 1 ). More interestingly, six adjacent linkers are packed together by π–π-stacking interactions to form an amazing six-molecule accumulation in the crystal structure. By virtue of high stability and luminescent properties, the as-synthesized sample not merely owns an excellent detectable ability but also possesses an outstanding selectivity for nitrofurans with remarkable recursitivity.

Until now, comparative studies on proton conductivity between organic ligands and related metal–organic frameworks (MOFs) have been very limited. Herein, a stable 2D Zn(II) MOF, [Zn(L)Cl] n ( 1 ), has been successfully synthesized by using a zwitterionic-type organic ligand, 2-(1-(carboxymethyl)-1 H -benzo[d]imidazol-3-ium-3-yl)acetate (HL). It is found that there are a large amount of free carboxyl groups and hydrogen bonds in the solid-state structure of HL, and a large number of chlorine ions are aligned in the channels of 1, which is favorable to the efficient proton transfer. Correspondingly, the proton conductivity values of 1 and HL are almost of the same order of magnitude under the same conditions. Moreover, the optimal σ value of 1 (4.72 × 10 –3 S/cm at 100 °C and 98% relative humidity) is almost four times higher than that (1.36 × 10 –3 S/cm) of the HL ligand. On the basis of the crystal data, SEM images, and calculated E a values, we discuss the differences on proton conductivities and conduction mechanisms of 1 and HL. This report provides an inspiration for the…

It is challenging to design and prepare difunctional photocatalysts for simultaneous photocatalytic wastewater purification and hydrogen (H 2 ) energy production. In this study, a novel ternary heterostructure pholocatalyst, ZnIn 2 S 4 @SiO 2 @TiO 2 (ZIS@SiO 2 @TiO 2 ) was successfully prepared by simple sol–gel and solvothermal methods. The SiO 2 nanospheres were used as a support to prevent the aggregation of TiO 2 nanoparticles efficiently. The SiO 2 @TiO 2 nanoparticles were uniformly inserted into the 2D-layered flowerlike ZnIn 2 S 4 to form a ternary heterostructure that can efficiently improve the separation and transportation of photoinduced electron–hole pairs. As expected, the 150%-ZIS@SiO 2 @TiO 2 nanocomposite exhibited an excellent rate of H 2 production under simulated sunlight (618.3 μmol g –1 h –1 ), which was 229 and 3.3 times higher than the binary SiO 2 @TiO 2 nanoparticles and pure ZnIn 2 S 4 . Furthermore, the degradation efficiency of methylene blue reached 99.7% during the H 2 production process. These findings provided possibilities to couple energy…

Polyoxometalates (POMs)-porphyrin hybrids can serve as multifunctional materials with fascinating photocatalytic and photovoltaic properties. However, most previous POM-porphyrin hybrids are synthesized relied on electrostatic interactions to form ion pairs, which is not stable enough and subject to leaching and poor electronic communication. To our knowledge, no specific crystalline structure of direct covalently tris-functionalized POM-porphyrin hybrids has been identified. Herein, we discover an unprecedented polyoxometalates (POMs)-based photoresponsive cluster, {V 6 O 13 [ZnC 61 H 58 N 5 O 4 ] 2 } 2– (denoted as V 6 –Zn-2Por), which can be synthesized by covalently grafting two tris-functionalized Zn-porphyrin ligands onto Lindqvist-type hexavanadate cluster using decavanadates (TBA) 3 [H 3 V 10 O 28 ] (denoted as V10, TBA = tetrabutylammonium cation) as precursor. Additionally, using tetraphenyl phosphonium as counterion, for the first time, a high-quality single crystal structure of the hybrid hexavanadate-porphyrin molecule is uncovered. Interestingly, the fluorescence…

Uranium is one of the principal raw materials in the nuclear industry, but if released into the natural environment, it also poses latent health risks to mankind. Therefore, there is an urgent need to develop a strategy that can concurrently detect and adsorb uranium to realize the sustainable development of nuclear power and protect the environment. In this work, a fluorescent zinc-based metal–organic framework ( HNU-50 ) was designed and synthesized for the effective detection and extraction of U(VI). The amide groups on N -pyridin-4-ylpyridine-4-carboxamide ligands and two uncoordinated carboxyl oxygen atoms on pyromellitic acid ligands in HNU-50 provide potential uranium-binding sites. Consequently, HNU-50 is competent of selectively and efficiently catching uranyl ions, achieving an optimum adsorption capacity of 632 mg/g. Additionally, the adsorption of U(VI) results in fluorescence quenching of HNU-50, thus allowing sensitive and selective detection of U(VI) by fluorescence change. Note that HNU-50 exhibits a considerably low detection limit of 1.2 × 10 –8 M for U(VI) in…

Structure determines properties, and properties determine applications, which is an important ideology of natural sciences. For optical materials, it is vital to lucubrate the corresponding relationship between the local crystal structure and luminescence properties for their design, synthesis, and application. This work reports a newly designed Y 2 Mg 2 Al 2 Si 2 O 12 (YMAS):Eu 3+ red phosphor, in which difunctional Eu 3+ ion is used as a red-light activator and spectroscopic probe. The qualitative and quantitative studies on the relationship between the local crystal structure and the luminescence properties of YMAS:Eu 3+ are performed experimentally and computationally, using the Y 3 Al 5 O 12 (YAG):Eu 3+ as contrast. Moreover, compared with YAG:Eu 3+, the newly designed YMAS:Eu 3+ has stronger luminescence, superior Commission Internationale de L’Eclairage chromaticity coordinates, a lower optimal doping concentration, and equally excellent thermal stability. The satisfactory color-rendering index of packaged white-light-emitting diodes demonstrates its potential performance as…

A new strategy to enhance the room temperature phosphorescence performance has been developed through hexanuclear Zn(II)-cluster-induced dense π-stacking in a metal-organic framework matrix. The synergistic effect of metal clusters and large overlap of π-conjugated dimers facilitate the phosphorescence emission, migration, and separation of charge carriers for excellent photocatalytic activity.

The rapid increase in the concentration of atmospheric carbon dioxide (CO 2 ) has resulted in undesirable environmental issues. Hence, selective CO 2 capture and utilization as C1 feedstock for the preparation of high-value chemicals and fuels has been considered as a promising step toward mitigating the growing concentration of atmospheric CO 2 . In this direction, herein we report rational construction of a Ag(I)-anchored sulfonate-functionalized UiO-66 MOF named as MOF-SO 3 Ag composed of CO 2 -philic sulfonate functionality and catalytically active alkynophilic Ag(I) sites for chemical fixation of carbon dioxide. The MOF-SO 3 Ag exhibits selective as well as recyclable adsorption of CO 2 with a high heat of adsorption energy ( Q st ) of 37.8 kJ/mol. On the other hand, the analogous MOF, UiO-66 doped with Ag(I), showed a lower Q st value of 30 kJ/mol, highlighting the importance of the sulfonate group for stronger interaction with CO 2 . Furthermore, the MOF-SO 3 Ag acts as an efficient heterogeneous catalyst for cyclic carboxylation of propargylic alcohols to generate…

Nickel ferrite (NiFe 2 O 4 ) and magnetite (Fe 3 O 4 ) are established earth-abundant materials and get tremendous attention because of magnetic and high photocatalytic activity. First we fabricated novel Fe 3 O 4 @20 wt % NiFe 2 O 4 /phosphorus-doped g-C 3 N 4 (M@NFOPCN) using a convenient simple coprecipitation method followed by calcination at 400 °C. Then M@NFOPCN composites were prepared by the in situ growth of Fe 3 O 4 nanorods and cubes on the surfaces of a porous agglomerated NFOPCN nanostructure, varying the weight percentage of Fe 3 O 4 . A series of characterizations like X-ray diffraction, UV–vis diffuse-reflectance spectroscopy, photoluminescence, Fourier transform infrared, thermogravimetric analysis–differential thermal analysis, vibrating-sample magnetometry, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy techniques confirm that changing weight percentage of M can constructively control the textural characteristics, internal strain, size of the crystals, and other aspects meant for photocatalytic activity. When M…

Toward the goal of clean and sustainable energy source, the development of a trifunctional electrocatalyst is a boon for energy storage and conversion devices such as regenerative fuel cells and metal-air batteries. MOF-derived semiconducting-metallic core–shell electrocatalyst Co 3 O 4 @Co/NCNT (NCNT = nitrogen-doped carbon nanotube), which was shown to catalyze oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), is also found to be an active electrocatalyst for hydrogen evolution reaction (HER) with a low overpotential of 171 mV. Here, the HER activity of Co 3 O 4 @Co/NCNT is presented and is shown as highly efficient and robust trifunctional electrocatalyst. The detailed theoretical calculation has found N-center of Co–N 4 moiety to be the H + binding active site and thus proves Co 3 O 4 @Co/NCNT to be active for HER. Further, the ORR and OER bifunctionality of Co 3 O 4 @Co/NCNT helped in fabricating secondary Zn-air battery with high power density of 135 mW/cm 2 . Also, an all-solid-state flexible and wearable battery with Co 3 O 4 @Co/NCNT as cathode and…