The 50 most-cited articles in Inorganic Chemistry, 2019

Although oxidation was deemed as the main factor responsible for the instability of MXenes in aqueous colloids, here we put forward and test a hypothesis about the central role of water as the primary factor. We show that water and related processes of MXene hydrolysis play the main role in the phenomena leading to complete transformations of 2D titanium carbide MXenes into titania in aqueous environments. To demonstrate the role of water, the stability of two MXenes, Ti 3 C 2 T x and Ti 2 CT x, has been systematically studied in aqueous and nonaqueous colloids exposed to oxygen and inert gas atmospheres. The calculated time constant for degradation of Ti 3 C 2 T x dispersed in anhydrous iso-propanol saturated with pure oxygen exceeds 5 years, in striking contrast to the same MXene dispersed in water, where more than a half of it would transform into titania even in an oxygen-less atmosphere over ∼41 days. A thinner Ti 2 CT x MXene showed similar behavior, albeit with shorter time constants in both solvents, correspondingly. UV–vis and Raman spectroscopy were used to analyze the…

-based metal-organic framework (MOF) with a rare tcj topology has been solvothermally synthesized and displays relatively good thermal and chemical stabilities. Interestingly, the MOF can sensitively and selectively sense acetylacetone (acac) via a fluorescence enhancement effect with a detection limit of 0.10 ppm and good reusability, which demonstrates the first example of a MOF-based turn-on fluorescent sensor for acac.

Molecule-based solid-state materials with long lifetimes could enable longer migration distances for excitons, which are beneficial for vast applications in optoelectronic field. Herein, we report a hexanuclear zinc cluster based MOF exhibits highly enhanced phosphorescence about 2 orders of magnitude in comparison with the pristine phosphor ligand. The combination of both experimental and computational results suggest that the {Zn 6 } cluster is very important for adjusting molecular conformations, packing arrangement, and photophysical properties of the organic phosphor ligands within the MOF matrix. Optoelectronic measurements reveal that the MOF-modified electrode is catalytically active to hydrogen evolution under light irradiation in neutral solution. Thus, our study provide an effective way to achieve low-cost metal-based phosphorescence MOF, expanding its further optoelectronic applications.

In the present work, a series of MOF-74 (Ni) materials with narrow micropore channels and abundant unsaturated metal sites was respectively prepared via hydrothermal (HT), condensation reflux (CE), and microwave-assisted (MW) methods. The physicochemical properties of synthesized materials were characterized by powder X-ray diffraction, N 2 -sorption, field-emission scanning electron microscopy, Fourier-transform infrared (FTIR), thermogravimetric (TG)/TG-FTIR, X-ray photoelectron spectroscopy, UV–vis–near infrared, NH 3 /CO 2 -temperature programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Their CO 2 /N 2 adsorption performances were evaluated by isotherm adsorption and dynamic adsorption experiments. We found that the MW is a rapid and facile protocol for the synthesis of MOF-74 (Ni) materials with highly efficient CO 2 capture capacity. The well-shaped MW-140 adsorbent with superior CO 2 adsorption capacity of 5.22 mmol/g at 25 °C can be obtained within 60 min by the MW process, almost 6 times higher than that of the commercial…

The restriction of sulfur content in fuels has become increasingly stringent as a result of the growing environmental concerns. Although several MOF-derived materials like POM@MOF composites have shown the ability to catalyze oxidative desulfurization (ODS), their catalytic activities inevitably obstructed by the encapsulated catalytic sites like POM due to the blockage of cavities. Therefore, MOFs with intrinsic and accessible catalytic sites are highly desirable for their applications in ultradeep ODS. Herein, four representative Zr-based MOFs (Zr-MOFs), namely, UiO-66, UiO-67, NU-1000, and MOF-808, were assessed for catalytic ODS. These MOFs were confirmed that they have peroxidase-like activity and can catalyze ODS with H 2 O 2 as oxidant. Among them, MOF-808 showed the highest catalytic activity and it can fully desulfurize dibenzothiophene (DBT) in a model gasoline with a S concentration of 1000 ppm under 40 °C within 5 min. An extremely low apparent Arrhenius activation energy (22.0 KJ·mol –1 ) and an extraordinarily high TOF value (42.7 h –1 ) were obtained, ranking MOF-808…

A cobalt(II) coordination polymer with an unusual 4,4,4-connected network was hydrothermally synthesized and observed with high thermal, solvent, and pH stabilities. This polymer can serve as the first dual-responsive fluorescent chemosensor for the selective detection of acetylacetone and Cr 2 O 7 2– ion (pH 3.0) in aqueous systems.

Organic–inorganic hybrid metal halides with zero-dimensional (0D) structure has emerged as a new class of light-emitting materials. Herein, a new lead-free compound (C 9 NH 20 ) 2 MnBr 4 has been discovered and a temperature-dependent phase transition has been identified for two phases (space group P 2 1 / c and C 2/ c ) in which individual [MnBr 4 ] 2– anions connect with organic cations, (C 9 NH 20 + ) (1-buty-1-methylpyrrolidinium + ), forming periodic structure with 0D blocks. A green emission band, peaking at 528 nm with a high photoluminescence quantum efficiency (PLQE) of 81.08%, has been observed at room temperature, which is originated from the 4 T 1 (G) to 6 A 1 transition of tetrahedrally coordinated Mn 2+ ions, as also elaborated by density functional theory calculation. Accordingly, a fast, switchable, and highly selective fluorescent sensor platform for different organic solvents based on the luminescence of (C 9 NH 20 ) 2 MnBr 4 has been developed. We believe that the hybrid metal halides with high PLQE and the exploration of these as a fluorescence sensor will expand…

The worsening pollution due to mercury species makes it inevitable to explore prospective versatile materials, which not only can detect mercury ions (Hg 2+ ) with high sensitivity but also possesses efficient capture and removal ability. In this study, a series of classic organic ligand-based luminescence MOFs materials with high oxidation state central metals (Al 3+, Zr 4+, Cr 3+, Fe 3+, and Ti 4+ ) were synthesized and were screened to achieve simultaneously Hg 2+ detection and removal through the strong coordination of amino groups or nitrogen centers with Hg 2+ and the intrinsic fluorescence intensity of MOFs regulated by the ligand-to-metal charge transfer (LMCT) effect. Among these checked materials, NH 2 -MIL-53(Al) exhibited the excellent ability for Hg 2+ detection with wide response interval (1–17.3 μM), low detection limit (0.15 μM), good selectivity, wide pH adaptation (4.0–10.0), and strong anti-interference ability. Meanwhile, the resultant NH 2 -MIL-53(Al) possessed an efficient removal capability toward Hg 2+, accompanied by a fast uptake kinetics (within 60 min)…

Enzyme-like metal-organic frameworks (MOFs) are currently one type of starring material in the fields of artificial enzymes and analytical sensing. However, there has been little progress in making use of the MOF structures based on the catalytically active metal center with multiple valences. Herein, we report a mixed-valence Ce-MOF (Ce-BPyDC) that can exhibit both oxidase-like and peroxidase-like activities. Ce-BPyDC was synthesized by a facile hydrothermal method, which preserves the rare coexistence of Ce(III) and Ce(IV) in the MOF structure. The enzymatic studies demonstrated the enzyme-like activities of Ce-BPyDC follow the Michaelis-Menten kinetics and are strongly dependent on temperature, pH, and reaction time. Ce-BPyDC was also revealed to exert high catalytic activity that could transcend horseradish peroxidase and other MOF nanozymes, due to the redox-active Ce(III)/Ce(IV) cycles inside. Furthermore, the simple synthesis, high nanozyme activity, and great stability of Ce-BPyDC motivated us to establish a colorimetric biosensing platform using…

Using density functional theory calculations, we explore the structural, electronic, and optical properties of the inorganic Ge-based halide perovskites AGeX 3 (A = Cs, Rb; X = I, Br, Cl) that can possibly be used as light absorbers. We calculate the lattice parameters of the rhombohedral unit cell with an R 3 m space group, frequency-dependent dielectric constants, photoabsorption coefficients, effective masses of charge carriers, exciton binding energies, and electronic band structures by use of PBEsol and HSE06 functionals with and without SOC effect. We also predict the absolute electronic energy levels with respect to the external vacuum level by using the (001) surfaces with AX and GeX 2 terminations, demonstrating their strong dependence on the surface terminations. The calculated results are found to be in reasonable agreement with the available experimental data for the cases of CsGeX 3, while for the cases of RbGeX 3 they are predicted for the first time in this work. We reveal that replacement of Cs with Rb can offer reasonable flexibility in optoelectronic properties…

The abolition of environmental pollutants and production of hydrogen (H 2 ) from water using a heterogeneous photocatalyst is a demanding science of the current scenario to solve the increasing environmental pollution and worldwide energy catastrophe in modern life. To validate this purpose, the design of low-cost and durable semiconductor-based photocatalysts with great light absorption capacity becomes the most challenging issue for researchers. Regarding this, herein the phosphotungstic acid (HPW)-anchored Zr 6 O 4 (OH) 4 (BDC) 6 (UiO-66) metal–organic framework (MOF), i.e., HPW@UiO-66, has been prepared by a hydrothermal method and is efficient, stable, and capable of harvesting solar energy toward the degradation of tetracycline hydrochloride (TCH) and H 2 production in the presence of a sacrificial donor. The ionic interaction between HPW and UiO-66 plays a key role toward the photostability and charge-transfer mechanism of the composite and is well characterized with X-ray diffraction, UV diffuse-reflectance spectroscopy, Fourier transform infrared, and X-ray photoelectron…

The highly porous luminescent metal–organic frameworks (MOFs) can act as fluorescent probes for the detection of nitro compounds and can also serve as containers and energy transfer platforms to construct the host–guest systems. Herein, two new three-dimensional MOFs with high porosity were prepared successfully by the electron-rich tetrakis(4-pyridylphenyl)ethylene (tppe) as ligands. Compound 1 shows the high sensitivity and selectivity toward nitro-antibiotics in an aqueous media, particularly showing the best detection efficiency for furazolidone (FZD) among the reported luminescent sensors. The highly efficient fluorescence quenching toward FZD may be attributed to the electron and energy transfer. Compound 2 has naphthalene-2,7-dicarboxylic acid (2,7-npd) and tppe as dual linkers, and the energy transfer between 2,7-npd and tppe leads to the emission band in a large scale. It is worth noting that the single-phased white-light materials can be obtained by the in situ encapsulation of different concentration of sulforhodamine 101 (SR101) into compound 2 matrix.

The nanozyme-based strategy is currently one of the frontiers in the detection of toxic heavy metal ions. However, the utilization of noble metal free nanozymes to construct an economically and environmentally sustainable methodology remains largely unknown. Here, chitosan-functionalized molybdenum(IV) selenide nanosheets (CS-MoSe 2 NS), greenly synthesized by an ionic liquid-assisted grinding method, were exploited for the colorimetric sensing of mercury ions (Hg 2+ ). The sensing principle was based on the activating effect of Hg 2+ on CS-MoSe 2 NS nanozyme activities, triggered by the in situ reduction of chitosan-captured Hg 2+ ions on a MoSe 2 NS surface. Using 3,3′,5,5′-tetramethylbenzidine (TMB) as a colorimetric indicator, the concentrations of activator-like Hg 2+ ions could be quantitatively and selectively monitored, reaching a limit of detection of 3.5 nM with the ultraviolet–visible spectrophotometer. In addition, the integration system of CS-MoSe 2 NS with a smartphone achieved a portable detection limit as low as 8.4 nM Hg 2+ within 15 min and showed high specificity…

Highly dense packing of chromophoric linkers is achieved in a novel pyrene-based metal–organic framework (MOF), [Zn(TBAPy) 1/2 (H 2 O) 2 ], induced by an ionic liquid. This MOF displays a quick response to visible-light irradiation (photocurrent density of up to 4.492 μA cm –2 ) and is capable of repetitive on–off photocurrent switching with a large on–off ratio (37.55).

We synthesized two new adenine-based Zn(II)/Cd(II) metal–organic frameworks (MOFs), namely, [Zn 2 (H 2 O)(stdb) 2 (5H-Ade)(9H-Ade) 2 ] n (PNU-21) and [Cd 2 (Hstdb)(stdb)(8H-Ade)(Ade)] n (PNU-22), containing auxiliary dicarboxylate ligand (stdb = 4,4′-stilbenedicarboxylate). Both MOFs were characterized by multiple analytical techniques such as single-crystal X-ray diffraction (SXRD), powder X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy, as well as temperature program desorption and Brunauer–Emmett–Teller measurements. Both MOFs were structurally robust and possessed unsaturated Lewis acidic metal centers [Zn(II) and Cd(II)] and free basic N atoms of adenine molecules. They were used as heterogeneous catalysts for the fixation of CO 2 into five-membered cyclic carbonates. Significant conversion of epichlorohydrin (ECH) was attained at a low CO 2 pressure (0.4 MPa) and moderate catalyst (0.6 mol %)/cocatalyst (0.3 mol %) amounts, with over 99% selectivity toward the ECH carbonate.…

Developing effective and simple one-pot synthetic strategies regarding the formation of heterojunction photocatalytic semiconductors remains an intense challenge in research pursuits. Further scheming of the p–n heterojunction has sustained renewed interest in catalysis, photocatalysis, energy storage, and conversion because they easily accelerate the bulk charge separation efficiency. Thus we have successfully designed a Au-MoS 2 /ZnIn 2 S 4 heterojunction photocatalyst for the first time by adopting a simple one-pot hydrothermal technique, followed by a deposition–precipitation method. By adjusting the mole ratio of Mo with that of Zn and In precursors, we have fabricated a MoS 2 /ZnIn 2 S 4 p–n heterojunction photocatalyst, and the established p–n heterojunction between MoS 2 and ZnIn 2 S 4 is demonstrated by various physicochemical and morphological characterizations. An interfacial junction is created between MoS 2 and ZnIn 2 S 4 at the depletion region via an in situ formation mechanism, leading to the enhancement of the charge separation through the p–n heterojunction and…

Carbon dots (CDs), as an effective bioimaging agent, have aroused widespread interest. With the increasing number of CDs used in photodynamic therapy (PDT), developing efficient CDs with multiple functions such as imaging and phototherapy has become a new challenge. Herein, a new type of copper-doped CDs (Cu-CDs) with a high fluorescence quantum yield of 24.4% was synthesized from a copper complex of poly(acrylic acid) through coordination between the carboxyl group and copper ions. Owing to their good solubility, bright fluorescence, and low cytotoxicity, the Cu-CDs can be used for fluorescence imaging in both the HeLa (human cervical cancer) cell line and SH-SY5Y (human neuroblastoma cells) multicellular spheroids (3D MCs). More importantly, the Cu-CDs show a high quantum yield of singlet oxygen ( 1 O 2; 36%), good photoinduced cytotoxicity, and effective inhibition of 3D MC growth. Therefore, the Cu-CDs can be used as a promising imaging-guided PDT agent. This study provides a new carbon-based nanomaterial for multifunctional photodiagnostic and therapeutic agents for biological…

Cationic framework materials capable of removing anionic pollutants from wastewater are highly desirable but relatively rarely reported. Herein, a cationic MOF (SCNU-Z1-Cl) possessing tubular channels with diameter of 1.5 nm based on Ni(II) and a nitrogen-containing ligand has been synthesized and applied to capture hazardous anionic contaminants from water. The SCNU-Z1-Cl exhibits high BET surface area of 1636 m 2 /g, and shows high hydrolytically stability in pH range from 4 to 10. Owing to the large tubular channels and the uncoordinated anions in the framework, the aqueous-phase anion-exchange applications of SCNU-Z1-Cl were explored with environmentally toxic oxo-anions including CrO 4 2–, Cr 2 O 7 2–, MnO 4 –, and ReO 4 –, and organic dyes. The adsorption of oxoanions exhibits high uptake kinetics and the adsorption capacities of CrO 4 2–, Cr 2 O 7 2–, MnO 4 –, and ReO 4 – are 126, 241, 292, and 318 mg/g, respectively, which were some of the highest values in the field of MOF/COF. In additional, the selectively is high when other concurrent anions are exist. The anionic dyes…

In this work, a new 3D metal–organic framework (MOF) {[Co 3 (μ 4 -tpa) 3 (μ-dapz)(DMF) 2 ]·2DMF} n (Co(II)-TMU-63; H 2 tpa = terephthalic acid, dapz = pyrazine-2,5-diamine, DMF = dimethylformamide) containing low-cost and readily available ligands was generated, fully characterized, and used as an electrode material in supercapacitors without the need for a calcination process. Thus, the synthesis of this material represents an economical and cost-effective method in the energy field. The crystal structure of Co(II)-TMU-63 is assembled from two types of organic building blocks (μ 4 -tpa 2– and μ-dapz ligands), which arrange the cobalt nodes into a complex layer-pillared net with an unreported 4,4,4,6T14 topology. The presence of open sites in this MOF is promising for studying electrochemical activity and other types of applications. In fact, Co(II)-TMU-63 as a novel electrode material when comparing with pristine MOFs shows great cycling stability, large capacity, and high energy density and so acts as an excellent supercapacitor (384 F g –1 at 6 A g –1 ). In addition, there was a…

A universal strategy is developed to construct metal-organic framework (MOF)-based superhydrophobic/superoleophilic materials by the reaction of activated MOFs and octadecylamine. In particular, S-MIL-101(Cr) composite can efficiently separate chloroform, toluene, petroleum ether, and n-hexane from water with excellent oil-water separation performance, with potential application in the environmental field.

In this work, we prepared two types of isostructural Ln 3+ -based metal–organic frameworks (LnMOFs) under solvothermal conditions, where two structurally similar pyridine-containing dicarboxylate ligands, 6-(4-carboxyphenyl)nicotinic acid and [2,2′-bipyridine]-5,5′-dicarboxylic acid, were used as the organic linkers. The as-synthesized LnMOF compounds were characterized using single-crystal X-ray diffraction (XRD), powder XRD, and thermogravimetric analysis. With the lanthanide co-doping approach, two mixed LnMOFs, Tb 0.95 Eu 0.05 cpna and Tb 0.95 Eu 0.05 bpydc, were obtained and evaluated for application as potential ratiometric luminescence thermometers. The temperature-dependent luminescence of the two materials was investigated, and their emission intensities, luminescence lifetimes, and thermometric parameters were compared. They exhibit an excellent S-shaped response for temperatures in the range of 25–300 K, with favorable relative sensitivity and temperature uncertainty. Moreover, their color changes from green at 25 K to red at 300 K, so that they are also suitable as…

Owing to the rapid increase of Hg(II) ions in water resources, the design and development of new adsorbents for Hg(II) removal are becoming a significant challenge in environmental protection. Herein, a thiol-functionalized metal–organic framework (SH-MiL-68(In)) was successfully prepared through a post-synthesis modification procedure, and the framework intactness and porosity were well maintained after this process. SH-MiL-68(In) exhibited selective adsorption performance for Hg(II) ions in water. Meanwhile, SH-MiL-68(In) also shows a high adsorption capacity (450 mg g –1 ), large adsorption rate (rate constant k 2 = 1.25 g mg –1 min –1 ), and good recycling of adsorption capacity toward Hg(II) ions. The excellent adsorption performance resulted from the strong binding interactions between -SH soft basic groups and Hg(II) soft acidic ions.

Low-dimensional organic–inorganic hybrid metal halides have emerged as broadband light emitters for phosphor-converted white light-emitting diodes (WLEDs). Herein, we report a new zero-dimensional (0-D) lead-free metal halide (PMA) 3 InBr 6 [PMA +: (C 6 H 5 CH 2 NH 3 ) + ] that crystallizes in the monoclinic system with P 2 1 / c space group. The structure consists of slightly distorted [InBr 6 ] 3– octahedra surrounded by organic PMA + cations. The direct band gap characteristic of (PMA) 3 InBr 6 was demonstrated by density functional theory calculation, and its relatively wide band gap of 3.78 eV was experimentally determined. Upon 365 nm ultraviolet light excitation, (PMA) 3 InBr 6 exhibited strong broadband orange luminescence with a full-width at half-maximum of ∼132 nm resulting from self-trapped exciton emission, and the photoluminescence quantum yield was determined to be ∼35%. A WLED fabricated by combining the orange-emitting (PMA) 3 InBr 6, a green phosphor Ba 2 SiO 4:Eu 2+, and a blue phosphor BaMgAl 10 O 17:Eu 2+ exhibited a high color-rendering index of 87.0. Our…

Three water-stable luminescent MOFs [Zn 4 (bptc) 2 (NMP) 3 (DMF)(H 2 O) 2 ] n ( 1-a ), [Cd 4 (bptc) 2 (NMP) 3 (DMF) 2 (H 2 O) 1 ] n ( 1-b ), and {[Zn 2 (bptc)(DMA)(H 2 O) 2 ]·(DMA) 2 ·H 2 O} n ( 2 ), possessing similar chemical components (M 2:L 1:Sol 3 ) and topology structures, were synthesized by solvents control. Their excellent sensing on iron(III) cation and nitroaromatic explosives (NACs) with great selectivity, sensitivity and a high K sv (4.54 × 10 4 for 1-b on PNP) were observed by quenching effects. Furthermore, Zn-MOFs exhibit interesting stimuli-responsive luminescence enhancement after the encapsulation of a series of IIIB cations stimulated different luminescent emitting and intensity enhancement through host–guest processes of the pores in MOFs, especially for two distinct responses of Zn-MOF on a Tb 3+ cation.

New coordination polymers of cobalt(II), namely, [Co(μ 4 -cpna)(H 2 O) 2 ] n ( 1 ), [Co(μ 3 -cpna)(phen)(H 2 O)] n · n H 2 O ( 2 ), [Co 3 (μ 4 -dppa) 2 (H 2 O) 6 ] n ·2 n H 2 O ( 3 ), and [Co 3 (μ 5 -dppa) 2 (μ-4,4′-bipy)(H 2 O) 2 ] n ·4 n H 2 O ( 4 ), have been generated under hydrothermal conditions from CoCl 2 ·6H 2 O, two different multifunctional pyridine-carboxylic acids {H 2 cpna: 5-(4-carboxyphenoxy)nicotinic acid; H 3 dppa: 5-(3,4-dicarboxylphenyl)picolinic acid}, and optional N, N -supporting ligands {phen: 1,10-phenanthroline; 4,4′-bipy: 4,4′-bipyridine} acting as mediators of crystallization. These Co(II) coordination polymers (CPs) have been obtained as stable crystalline materials and characterized by conventional solid-state techniques, including X-ray crystallography. The obtained products are 3D metal–organic frameworks (MOFs 1 and 4 ) or 2D coordination polymers (CPs 2 and 3 ). Analysis of the topologies of simplified nets has revealed the sra ( 1 ), fes ( 2 ), and 3,4L13 ( 3 ) networks, in addition to a very complex topologically unique framework in 4 . An…

Rapid and low-cost synthesis of metal–organic frameworks (MOFs) are very meaningful for their future practical application. In the present study, a Zr-based ultrastable MOF, UiO-66-NH 2, was successfully synthesized by electrochemical method using metal Zr as the metal source at room temperature and atmospheric pressure. The effects of the reaction conditions, including the ratio of solvent (electrolyte), the applied voltage and different reaction time, on the crystallinity, morphology, and synthesis rate of the product were fully investigated. The results confirm that electrochemically synthesized UiO-66-NH 2 under the optimized condition possesses apparent merits such as high crystallinity, uniform morphology and high porosity. Moreover, the electrochemical synthesis method of UiO-66-NH 2 is promising for the large-scale and economical synthesis of nanoscale product to gramme degree. Interestingly, the resulting UiO-66-NH 2 synthesized by this electrochemical method exhibits more excellent performance for the fluorescence detection of Fe 3+ ions in water (detection limit of 10 –8…

Explicit control of the crystalline phases and morphology of semiconducting BiVO 4 crystals has been successfully synthesized via microwave-hydrothermal condition (MW-HT) without requiring any template/surfactant, doping of metal ions, and altering pH of reaction solution. Unambiguously, the crystalline phase of BiVO 4 crystal has transformed from tetragonal zircon type ( tz ) to monoclinic scheelite ( m ) via mixed-phase ( m - tz ) by altering microwave-irradiation time at fixed microwave-irradiation power (800 W) without changing any precursor concentrations throughout the reaction. X-ray diffraction and Rietveld refinement studies confirmed the phase transformation of BiVO 4 crystals that occurs by controlling the irradiation time (10–22 min) and temperature (116–195 °C). The changes in VO 4 3– tetrahedron bond strength and bond length attributed to phase transitions in BiVO 4 crystals were corroborated by Raman spectra. Field emission scanning electron microscope revealed the sequential growth and rational morphological evolution of spherical-shaped zircon type tz -BiVO 4…

Two types of infrared fluoride phosphors, Cr 3+ -doped K 3 AlF 6 and K 3 GaF 6, were developed in this research. The K 3 Al 1– x F 6: x Cr 3+ and K 3 Ga 1– y F 6: y Cr 3+ fluoride phosphors were proven to be pure phase via X-ray diffraction refinement, which demonstrated that the procedure can be applied to large-scale production. Electron paramagnetic resonance measurements indicated that Cr 3+ ions in cubic with respect to noncubic are coupled better with K 3 GaF 6 than with K 3 AlF 6 . The main differences between these two phosphors, the site symmetry and pressure behavior of the spectra, were obtained in temperature- and pressure-dependent spectra. According to the calculation results, Cr 3+ in fluorine coordination at ambient pressure indicates an intermediate crystal field. For the phosphor-converted light-emitting diodes (LEDs) fabricated from these two phosphors, the spectral range is from 650 to 1000 nm, which resulted in a radiant flux of 7–8 mW with an input power of 1.05 W. The research reveals detailed luminous properties, which will lead to a new way of studying Cr 3+…

Recently, phenanthroline-based ligands have received increasing attention due to their excellent separation capabilities for trivalent actinides over lanthanide. In this work, we designed a soft–hard donor combined tetradentate phenanthroline-based extractant, tetraethyl (1,10-phenanthrolin-2,9-diyl)phosphonate (C2-POPhen), for the selective separation of trivalent Am(III) over Ln(III) from HNO 3 media. The solvent extraction and complexation behaviors of Am(III) and Ln(III) by C2-POPhen were investigated both experimentally and theoretically. C2-POPhen could selectively extract Am(III) over Eu(III) with an extremely fast extraction kinetics. NMR titration studies suggest that only 1:1 complexes of Ln(III) with C2-POPhen formed in CH 3 OH in the presence of a significant amount of nitrate, while both 1:1 and 2:1 complexes species could form between C2-POPhen and Ln(III) perchlorate in CH 3 OH without nitrate ions. The stability constants for the complexation of Am(III) and Ln(III) with C2-POPhen in CH 3 OH were determined by spectrophotometric titrations and the Am(III) complexes…

A series of eight bis(thiosemicarbazone) ligands and 16 of their respective copper(II) and zinc(II) complexes containing a combination of hydrogen, methyl, pyridyl, phenyl, and/or ethyl substituents at the diimine position of the ligand backbone were synthesized and characterized. The objective of this study was to identify the structure–activity relationships within a series of analogues with different substituents at the diimine position of the backbone and at the terminal N atom. The Cu(II) complexes Cu(GTSM 2 ), Cu(GTSCM), Cu(PyTSM 2 ), Cu(EMTSM 2 ) and Cu(PGTSM 2 ) demonstrated a distorted square planar geometry, while the Zn(II) complexes Zn(ATSM 2 )(DMSO), Zn(PyTSM 2 )(DMSO), and Zn(PGTSM 2 )(H 2 O) formed a distorted square pyramidal geometry. Cyclic voltammetry showed that the Cu(II) complexes display quasi-reversible electrochemistry. Of the agents, Cu(II) glyoxal bis(4,4-dimethyl-3-thiosemicarbazone) [Cu(GTSM 2 )] and Cu(II) diacetyl bis(4,4-dimethyl-3-thiosemicarbazone) [Cu(ATSM 2 )] demonstrated the greatest antiproliferative activity against tumor cells. Substitutions…

Highly porous, polyhedral metal–organic frameworks (MOFs) of Co(II)/Ni(II), {[M 6 (TATAB) 4 (DABCO) 3 (H 2 O) 3 ]·12DMF·9H 2 O} n (where M = Co(II) ( 1 )/Ni(II) ( 2 ), H 3 TATAB = 4,4′,4″- s -triazine-1,3,5-triyl-tri- p -aminobenzoic acid, and DABCO = 1,4-diazabicyclo[2.2.2]octane) have been synthesized solvothermally. Both MOFs 1 and 2 show a 2-fold interpenetrated 3D framework structure composed of dual-walled cages of dimension ∼ 30 Å functionalized with a high density of Lewis acidic Co(II)/Ni(II) metal sites and basic -NH- groups. Interestingly, MOF 1 shows selective adsorption of CO 2 with high heat of adsorption ( Q st ) value of 39.7 kJ/mol that is further supported by theoretical studies with computed binding energy (BE) of 41.17 kJ/mol. The presence of the high density of both Lewis acidic and basic sites make MOFs 1 / 2 ideal candidate materials to carry out co-catalyst-free cycloaddition of CO 2 to epoxides. Consequently, MOFs 1 / 2 act as excellent recyclable catalysts for cycloaddition of CO 2 to epoxides for high-yield synthesis of cyclic carbonates under…

Design and synthesis of non-noble metal electrocatalysts with high activity and durability for the electrolysis of water is of great significance for energy conversion and storage. In this work, we prepared a series of Fe-doped MoS 2 nanomaterials by simple one-pot solvothermal reactions of (NH 4 ) 2 MoS 4 with FeCl 3 ·6H 2 O. An optimized working electrode of Fe-MoS 2 -5 displayed high hydrogen evolution reaction (HER) activity with a relatively small overpotential of 173 mV to achieve a current density of 10 mA cm –2 in 0.5 M H 2 SO 4, along with no significant change in catalytic performance even after 1000 cyclic voltammetry (CV) cycles. Fe-MoS 2 nanoparticles on nickel foam (NF; denoted as Fe-MoS 2 /NF) exhibited an overpotential of 230 mV at 20 mA cm –2 for the oxygen evolution reaction (OER) and 153 mV at 10 mA cm –2 for the HER in 1.0 M KOH electrolyte. Fe-MoS 2 /NF was stable for more than 140 h under these conditions. Furthermore, the two electrode system of Fe-MoS 2 /NF (anode)//Fe-MoS 2 /NF (cathode) electrodes demonstrated excellent electrocatalytic activity toward…

species in terms of the formation, characterization, and DFT-based proposals to shed light on the characteristics of the intriguing oxidatively active species.

By using the mixed-linker strategy, a new pillar-layered luminescence Zn-LMOF ( JLU-MOF71 ) ([Zn 2 Na 2 (TPHC)(4,4-Bipy)(DMF)]·8H 2 O) (TPHC = [1,1′:2′,1″-terphenyl]-3,3″,4,4′,4″,5′-hexacarboxylic acid, 4,4-bipy = 4,4-bipyridine, DMF = N, N -dimethylformamide) was successfully synthesized and structurally characterized. JLU-MOF71 is constructed by the 4,4-bipy pillars and 2D layers which consist of Zn 2+ and TPHC ligands, and displays a rare fsh topology. Benefiting from the uncoordinated carboxylate sites in the framework, JLU-MOF71 not only can sensitively detect trace amounts of individual Fe 3+ and 2,4,6-trinitrophenol (TNP) through luminescence quenching but also exhibits high selectivity when other competing analytes exist. Besides, TNP can also be effectively monitored with the help of the shifting direction of luminescent spectra (red shift) which has rarely been reported before. On the basis of the aforementioned, JLU-MOF71 can be considered as a potential luminescence sensor for detecting Fe 3+ and TNP.

Pollution of water resources by antibiotics is a growing environmental concern. In this work, nanocomposites of g-C 3 N 4 @Ni–Ti layered double hydroxides (g-C 3 N 4 @Ni–Ti LDH NCs) with high surface areas were synthesized through an optimized hydrothermal method, in the presence of NH 4 F. Application of various characterization techniques unraveled that the prepared nanocomposites are composed of porous Ni–Ti LDH nanoparticles and hierarchical g-C 3 N 4 nanosheets. Further, these NCs were employed for photocatalytic and sonophotocatalytic removal of amoxicillin (AMX), as a model antibiotic, from aqueous solutions. In addition, sonocatalysis was performed. It was found out that the g-C 3 N 4 @Ni–Ti LDH NCs outperform their pure g-C 3 N 4 and Ni–Ti LDH components in photocatalytic degradation of AMX under visible light irradiation. Also, the following order was determined for efficiency of the three adopted processes: sonocatalysis < photocatalysis < sonophotocatalysis. Furthermore, variation of the sonophotocatalysis conditions specified 500 W light intensity, 9 s on/1 s off…

Abstract We report a comparative study of the binding of I2 (iodine) in a pair of redox-active metal–organic framework (MOF) materials, MFM-300(VIII) and its oxidized, deprotonated analogue, MFM-300(VIV). Adsorption of I2 in MFM-300(VIII) triggers a host-to-guest charge-transfer, accompanied by a partial (∼30%) oxidation of the VIII centers in the host framework and formation of I3– species residing in the MOF channels. Importantly, this charge-transfer induces a significant enhancement in the electrical conductivity (Δσ = 700000) of I2@MFM-300(VIII/IV) in comparison to MFM-300(VIII). In contrast, no host–guest charge-transfer or apparent change in the conductivity was observed upon adsorption of I2 in MFM-300(VIV). High-resolution synchrotron X-ray diffraction of I2@MFM-300(VIII/IV) confirms the first example of self-aggregation of adsorbed iodine species (I2 and I3–) into infinite helical chains within a MOF.

The local symmetry of a Eu 3+ ion has a crucial effect on its luminescence properties. In this work, we show that the red/orange ratio in the emission of Eu 3+ -doped MgIn 2 P 4 O 14 phosphors is tunable by adjusting the Eu 3+ concentrations, due to the change in the local symmetry of metal ions. The substitution of Eu 3+ for In 3+ lowers the distortion in the lattice of monoclinic MgIn 2 P 4 O 14, and an increase in Eu 3+ doping concentration causes the metal ion sites to shift closer to an inverse center, leading to a reversal of the relative emission intensity of a magnetic dipole transition to an electric dipole transition. Meanwhile, the higher asymmetry of metal ion sites occupied by Eu 3+ in MgIn 2 P 4 O 14 makes the luminescence less thermally stable than that in Mg 3 In 4 P 6 O 24 .

The detection of hypochlorite (ClO – ) content in tap water is extremely important because excess amounts of hypochlorite can convert into highly toxic species and inadequate amounts of hypochlorite cannot fully kill bacteria and viruses. Although several metal–organic frameworks (MOFs) have been successfully employed as fluorescent sensors for hypochlorite detection, all these sensors are based on single emission that responds to the dose of hypochlorite. Ratiometric sensors are highly desirable, which can improve the sensitivity, accuracy, and reliability via self-calibration. Herein, a nanoscale dual-emission multivariate 5-5-Eu/BPyDC@MOF-253-NH 2 was synthesized by sequential mixed-ligand self-assembly and postsynthesis method. Among the two emission bands of 5-5-Eu/BPyDC@MOF-253-NH 2, the strong blue emitting derived from ligands is sensitive to hypochlorite, while the red emitting derived from Eu(III) almost keeps invariable. Therefore, 5-5-Eu/BPyDC@MOF-253-NH 2 was exploited as a fluorescent ratiometric nanosensor for “on–off” sensing of hypochlorite. Notably, the proposed…

MOFs present potential application in electrocatalysis. The structure–activity of the Ni-MOFs with different morphologies, nanowires, neurons, and urchins is systemically investigated. The Ni-MOFs were controllably synthesized via the facile solvothermal method. Among them, the Ni-MOF nanowires are endowed with the highest electrocatalytic activity due to the unique structure, more exposed active sites, lower charge transfer resistance, and the fast and direct electron transfer in 1D structures. The typical morphology of the Ni-MOF nanowires is ca . 10 nm in diameter and several micrometers in length. When employed as an electrocatalyst in urea oxidation reaction, it exhibits a lower overpotential than and superior stability to the Ni-MOFs with other morphologies. Ni-MOF nanowires require a potential of ∼0.80 V (vs Ag/AgCl) to obtain 160 mA cm –2 . In addition, after continuous electrocatalyzing for 3600 s at 0.40 V (vs Ag/AgCl), the current density retention of Ni-MOF nanowires could still reach more than 60% (>12 mA cm –2 ), which demonstrates Ni-MOF nanowires as promising…

Rationally designed multiple hydroxyl-group-based chemosensors L1 – L4 containing arene-based fluorophores are presented for the selective detection of Al 3+ and Ga 3+ ions. Changes in the absorption and emission spectra of L1 – L4 in ethanol were easily observable upon the addition of Al 3+ and Ga 3+ ions. Competitive binding studies, detection limits, and binding constants illustrate significant sensing abilities of these chemosensors with L4, showing the best results. The interaction of Al 3+ /Ga 3+ ions with chemosensor L4 was investigated by fluorescence lifetime measurements, whereas Job’s plot, high-resolution mass spectrometry, and 1 H NMR spectral titrations substantiated the stoichiometry between L4 and Al 3+ /Ga 3+ ions. The solution-generated [ L -M 3+ ] species further detected pyrophosphate ion (PPi) by exhibiting emission enhancement and a visible color change. The binding of Al 3+ /Ga 3+ ions with chemosensor L4 was further supported by density functional theory studies. Reversibility for the detection of Al 3+ /Ga 3+ ions was achieved by utilizing a suitable proton…

Here we describe, a simple solution and solid-state sensor for the ultrasensitive detection of Hg(II) ions in both standardized and environmental samples through changes of fluorescence intensity of a zinc-based metal–organic framework (MOF). The MOF is highly water stable in a wide pH range from 4 to 11. The lower detection limit of Hg 2+ is 10 –11 M with a very high binding constant of 1.011 × 10 9 M –1 s –1 . It also exhibits a high selectivity toward mercury ion in the presence of other interfering metal ions. The MOF is found to retain its efficiency in detecting mercury ion in spiked environmental water samples.

The research on luminescent lanthanide-functionalized covalent organic framework (COF)-based hybrid materials has not been reported so far. When a straightforward functionalized modification strategy is employed, a chemical stable Eu 3+ -modified COF hybrid material, [email protected], is first developed. The functional process does not affect the size and shape of TpPa-1, but after the introduction of Eu 3+, [email protected] as a fluorescence sensor exhibits a turn-on response toward levofloxacin. Eu 3+ plays a bridge role in the whole detection system, and TpPa-1 serves as a host matrix to provide protection for the introduced Eu 3+ . This reusable sensor shows strong pink-white and yellow emissions toward the high and low concentration ranges of levofloxacin, respectively. It displays excellent sensitivity and fast response to levofloxacin within 1 min, while refraining from the interference of other coexisting species in serum and urine. The good selectivity and high antidisturbance lead [email protected] to be successfully applied in serum and urine systems for sensing…

It is deemed as a desired approach to utilize solar energy for the conversion of CO 2 into valuable products, and the majority of the MOFs-based photocatalytic reductions of CO 2 have focused on formic acid (HCOOH) production with an organic solvent as the reaction medium. Herein, we report a solvent-free reaction route for the photoreduction of CO 2 catalyzed by Fe-MOFs, namely, NH 2 -MIL-53(Fe) [(Fe(OH)(NH 2 –BDC)]•G, NH 2 -MIL-88B(Fe) [Fe 3 O(H 2 O) 3 (NH 2 –BDC) 3 ]Cl•G, and NH 2 -MIL-101(Fe) [Fe 3 O(H 2 O) 3 (NH 2 –BDC) 3 ]Cl•G (NH 2 –BDC = 2-aminoterephthalic acid; G = guest and/or solvent molecules). Compared with the orthodox reaction route, the present out-of-the-way photocatalytic reduction of CO 2 with superior selectivity to CO occurs at the gas–solid interface. The reaction procedure is environmentally friendly and provides a possibility to address the CO 2 emission problem. Importantly, NH 2 -MIL-101(Fe) shows the highest photocatalytic activity among these Fe-MOFs due to its efficient charge separation and electron transfer.

Because of its extreme toxicity, the determination of Hg 2+ in aqueous solution is an important subject for human health and environmental monitoring. In this study, a novel UIO-66-type metal–organic framework (MOF) doped with Eu 3+ (isophthalic acid and 2,6-pyridinedicarboxylic acid and zirconium chloride served as the organic connectors and metal precursor, respectively) was prepared by a hydrothermal method and postsynthetic modification. The obtained lanthanide MOFs exhibited good photothermal and fluorescence stability in aqueous solution. As a luminescent probe, dispersions of the material can specifically recognize Hg 2+ in many ions and have a detection limit of 8.26 nM. This novel lanthanide MOF shows great potential applications for biosensing, imaging, environmental analysis, and so on.

Abstract An exceptionally stable metal–organic framework based on one-dimensional (1D) TbIII chains with significant green emission under excitation energy, {[Tb­(TATMA)­(H2O)·2H2O}n (namely, 1), has been fabricated successfully under hydrothermal conditions. By virtue of the spectral overlap between the absorbance spectra of nitrofurans (NFAs) and the excitation spectrum of MOF 1, the resultant sample exhibits outstandingly sensitive and selective luminescence detectability for NFT (Ksv = 3.35 × 104 M–1) and NFZ (Ksv = 3.00 × 104 M–1) by quenching phenomenon. More importantly, it can detect NFAs in water from bovine serum samples. The portable MOF film can be easily prepared and used with excellent stability and recursitivity.

Abstract The fabrication of a multifunctional sensor together with a widening temperature-sensing range is an essential challenge in optical thermometers especially for trivalent lanthanide-doped materials. Herein, we design a wide range, highly sensitive, and multifunctional thermometer by exploiting the emission spectrum of Eu3+ ions, and further detailed discussion has been made on the new temperature-sensing mechanism. The sensor can be operated between 358 and 548 K with a maximum relative sensitivity (Sr) of 0.93% K–1 at 358 K, which is higher than that of most temperature-sensing materials. A paramount superiority is that the calibration parameter can be directly calculated from the single Eu3+ emission spectrum, avoiding the demand of other calibrations, which realizes the coexistence of a simple structure and high precision. Furthermore, other up-conversion thermometers based on Er3+/Ho3+/Yb3+ co-doped Ba2TiGe2O8 (BTG) phosphors as well as the down-conversion thermometer based on Eu3+-doped Ba2TiGe2O8 (BTG:Eu3+) phosphor have been synthesized for comparison, and the results…

Abstract The rational design of efficient and durable oxygen evolution reaction (OER) is important for energy conversion and storage devices. Here, we develop a two-step calcination method to prepare cobalt nanoparticles uniformly dispersed on perovskite oxide nanofibers and to tune oxygen vacancies in perovskite LaMn0.75Co0.25O3−δ nanofibers. The obtained product shows enhanced activity toward OER. In particular, the oxygen deficient LMCO-2 catalyst prepared by a two-step calcination shows excellent OER performance that is 27.5 times that of the LMO catalyst and is comparable to that of the commercial RuO2 catalyst. It also demonstates good stability because of its novel structure, abundant oxygen vacancies, and larger number of metal ions with a high oxidation state. As an air electrode for a flexible zinc–air battery, the cell with the LMCO-2 catalyst delivers a higher power density of 35 mW cm–2 and excellent cycling stability for 70 h. Moreover, the cell exhibits excellent flexibility under different bending conditions.

Manipulating the distribution of rare earth activators in multiple cations’ sites of phosphor materials is an essential step to obtain tunable emission for the phosphor-converted white-light-emitting diodes (pc-WLEDs). However, it remains the challenge to realize the photoluminescence tuning in the single-phased phosphor with single activator, due to the uncertain location of doped ions and adjustable crystallographic sites. Herein we reported the β-Ca 3 (PO 4 ) 2 -type solid solution phosphors (Ca 8.98– x Sr x )MgK(PO 4 ) 7:2%Eu 2+ ( x = 0–8.98) and the effects of replacing Ca 2+ by Sr 2+ ions on the phase structures and color-tunable emission were investigated in detail. Tunable color emission has been realized by manipulating the redistribution of Eu 2+ ions among different cation sites with adjustable chemical environment, and the related mechanism on the local structures has been discussed. The high R a (85) and low color temperature (CCT) (4465 K) values of the as-fabricated WLEDs lamp indicate that (Ca 4.98 Sr 4 )MgK(PO 4 ) 7:2%Eu 2+ can act as a promising white-emitting…

Among two-dimensional (2D) materials, such as graphene, a new family of 2D anisotropic carbides and nitrides of early transition metals (MXenes) is very interesting because of the potential applications in electronics, medicine, and photocatalysis. In this paper, preparation, morphostructural characterization, band gaps determination, and salicylic acid photodegradation ability of Ti 2 C MXene and six nanocomposites consisting of the MXene modified by TiO 2, Ag 2 O, Ag, PdO, Pd, and Au are reported. It was confirmed using electron diffraction studies, energy dispersive X-ray spectroscopy, and high-resolution transmission microscopy that metals and metal oxides occur on the MXene flakes as nanoparticles in a shape of spots. The band gaps determined experimentally using Tauc’s method are placed in the region of 0.90–1.31 eV. In recent years, the method of photocatalytic decomposition of pollutants using semiconductor photocatalysts and UV–vis energy has become increasingly important. The MXene based nanocomposites revealed high activity in the salicylic acid (SA) photodegradation…

Postsynthetic modification represents an efficient strategy for the fabrication of tunable metal–organic frameworks (MOFs) and derived high-performance functional materials. Herein, we report the synthesis of a mixed-linker zinc(II)-based double-layered MOF ( dlMOF ) with dual-emissive luminescence, which was further applied as a host matrix to fabricate highly tunable Ln@dlMOF materials (Ln = Eu, Tb, Eu/Tb). The emission characteristics of these materials can be readily modulated over a wide spectrum, including white light emission, by simply tuning the Eu 3+ /Tb 3+ molar ratio in EuTb@dlMOF . Furthermore, by virtue of the difference in thermal sensitivity between triple-emissive sources, the Eu 3+ /Tb 3+ -codoped thermometer EuTb@dlMOF exhibits real-time successive chromogenic switches from red (room temperature) to white (intermediate temperature) to blue/green (cryogenic temperature) emission in a wide temperature region. The versatile performance and the facile assembly from easily available linkers suggest that postsynthetic lanthanide encapsulation represents an efficient…