Search Results (14)

Considering the importance of organic functionalization of MOFs, we here report a simple, tunable and efficient one-step post-modification procedure for introducing amino and carboxylic groups into the mesoporous metal–organic framework Al- and Cr-MIL-101-NH₂ based on its reaction with alkyl bromides. This procedure allows also access to polyfunctionalized MIL-101 decorated with both carboxylic and primary amino groups. Other chemical functions, such as alcohols and alkynes, were also successfully introduced by this method. Full article

Compared to traditional liquid electrolytes, solid electrolytes have received widespread attention due to their higher safety. In this work, a vinyl functionalized metal–organic framework porous material (MIL-101(Cr)-NH-Met, noted as MCN-M) is synthesized by postsynthetic modification. A novel three-dimensional hybrid gel composite solid electrolyte (GCSE-P/MCN-M) is successfully prepared via in situ gel reaction of a mixture containing multifunctional hybrid crosslinker (MCN-M), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), ethylene carbonate (EC), diethylene glycol monomethyl ether methacrylate (EGM) and polyethylene (vinylidene fluoridee) (PVDF). Benefiting from the excellent mechanical properties, rich pore structure, and numerous unsaturated metal sites of GCSE-P/MCN-M, our GCSE-P/MCN-M exhibits excellent mechanical modulus (953 MPa), good ionic conductivity (9.3 × 10⁻⁴ S cm⁻¹) and wide electrochemical window (4.8 V). In addition, Li/LiFePO₄ batteries based on GCSE-P/MCN-M have also demonstrated excellent cycling performance (a high-capacity retention of 87% after 200 cycles at 0.5 C). This work provides a promising approach for developing gel solid-state electrolytes with high ion conduction and excellent safety performance. Full article

Industrialization activities have increased the discharge of wastewater that is polluted with hexavalent chromium (Cr(VI)), posing risks to ecosystems and humans. The photocatalytic reduction of Cr(VI) is viewed as a promising method for the removal of Cr(VI) species. However, developing photocatalysts with the desired catalytic activity, recyclability, and reusability remains a challenge. Herein, a composite aerogel was designed and fabricated with a Ti-based metal–organic framework (MIL-125-NH₂) and carboxylated nanocellulose. MIL-125-NH₂ presents a strong visible-light response, and the interactions between the amino groups of MIL-125-NH₂ and the carboxyl groups of cellulose produce a strong interface affinity in the composites. The as-prepared aerogels exhibited a micro/macroporous structure. At an optimal MIL-125-NH₂ loading of 55 wt%, the MC-5 sample showed a specific surface area of 582 m²·g⁻¹. MC-5 achieved a photocatalytic Cr(VI) removal efficiency of 99.8%. Meanwhile, the aerogel-type photocatalysts demonstrated good stability and recycling ability, as MC-5 maintained a removal rate of 82% after 10 cycles. This work sheds light on the preparation of novel photocatalysts with three-dimensional structures for environmental remediation. Full article

Halide perovskite has shown great potential in photocatalysis owing to its diversity, suitable energy band alignment, rapid charge transfer, and excellent optical properties. However, poor stability, especially under humid conditions, hinders their practical application in photocatalysis. In this work, we report the encapsulation of inorganic–organic hybrid perovskite QDs into MIL-101(Cr) through an in situ growth strategy to prepare a series of MAPbBr₃@MIL-101(Cr) (MA = CH₃NH₃⁺) composites. The perovskite precursors, i.e., MABr and PbBr₂, were successively introduced into the pores of MOF, where the perovskite quantum dots were self-assembled in the confined environment. In photocatalytic CO₂ reduction, 11%MAPbBr₃@MIL-101(Cr) composite displayed the best performance among the composites with a total CO and CH₄ yield of 875 μmol g⁻¹ in 9 h, which was 8 times higher than that of the pure MAPbBr₃. Such high gas production efficiency could be maintained for 78 h at least without structural and morphologic decomposition. The remarkable stability and catalytic activity of composites are mainly due to the synergistic effect and improved electron transfer between MAPbBr₃ and MIL-101(Cr). Moreover, these composites revealed a novel mechanism, showing switched CH₄ selectivity with the controlling of the perovskite location and contents. Those with perovskites encapsulated in the mesopores of MIL-101(Cr) were more preferential for CO production, while those with perovskites encapsulated in both meso- and micropores could produce CH₄ dominantly. Full article

Metal–organic frameworks (MOFs) are new porous materials composed of metal centers and organic ligand bridges, which received great attention in the field of photocatalysis. In this work, Ag₂CrO₄@MIL–125(Ti)–NH₂ (denoted as AgCr@M125) Z–scheme heterojunctions were synthesized via a simple microemulsion method, by which highly dispersed nano–sized Ag₂CrO₄ can be anchored uniformly on the surfaces of porous MIL–125(Ti)–NH₂ (denoted as M125). Compared with pure M125 and Ag₂CrO₄, the as–prepared AgCr@M125 hybrids show significant photocatalytic efficiency against inactivated Staphylococcus aureus (S. aureus), reaching over 97% inactivation of the bacteria after 15 min of visible light irradiation. Notably, the photocatalytic activity of the obtained 20%AgCr@M125 is about 1.75 times higher than that of AgCr–M125, which was prepared via a traditional precipitation method. The enhanced photocatalytic antibacterial activity of the AgCr@M125 photocatalytic system is strongly ascribed to a direct Z–scheme mechanism, which can be carefully discussed based on energy band positions and time–dependent electron spin response (ESR) experiments. Our work highlights a simple way to enhance the antibacterial effect by coupling with Ag₂CrO₄ and M125 via a microemulsion–assisted strategy and affords an ideal example for developing MOFs–based Z–scheme photocatalysts with excellent photoactivity. Full article

In this study, a flower–like BiVO₄/MIL–101–NH₂ composite is synthesized by a facile and surfactant–free process. The –COO⁻–Bi³⁺ ionic bond construction was conductive to enhance the interface affinity between BiVO₄ and MIL–101–NH₂. Due to the highly efficient light capture and sufficient electron traps induced by oxygen vacancies and the formation of a heterostructure, the improved separation and transportation rates of charge carriers are realized. In addition, the MIL–101–NH₂/BiVO₄ composite is favorable for Cr(VI) photocatalytic removal (91.2%). Moreover, FNBV–3 (Fe/Bi = 0.25) also exhibited an excellent reusability after five cycles. Full article

The relatively stable MOFs Alfum, MIL-160, DUT-4, DUT-5, MIL-53-TDC, MIL-53, UiO-66, UiO-66-NH₂, UiO-66(F)₄, UiO-67, DUT-67, NH₂-MIL-125, MIL-125, MIL-101(Cr), ZIF-8, ZIF-11 and ZIF-7 were studied for their C₆ sorption properties. An understanding of the uptake of the larger C₆ molecules cannot simply be achieved with surface area and pore volume (from N₂ sorption) but involves the complex micropore structure of the MOF. The maximum adsorption capacity at p p₀⁻¹ = 0.9 was shown by DUT-4 for benzene, MIL-101(Cr) for cyclohexane and DUT-5 for n-hexane. In the low-pressure range from p p₀⁻¹ = 0.1 down to 0.05 the highest benzene uptake is given by DUT-5, DUT-67/UiO-67 and MIL-101(Cr), for cyclohexane and n-hexane by DUT-5, UiO-67 and MIL-101(Cr). The highest uptake capacity at p p₀⁻¹ = 0.02 was seen with MIL-53 for benzene, MIL-125 for cyclohexane and DUT-5 for n-hexane. DUT-5 and MIL-101(Cr) are the MOFs with the widest pore window openings/cross sections but the low-pressure uptake seems to be controlled by a complex combination of ligand and pore-size effect. IAST selectivities between the three binary mixtures show a finely tuned and difficult to predict interplay of pore window size with (critical) adsorptive size and possibly a role of electrostatics through functional groups such as NH₂. Full article

Severe environmental pollution is caused by the massive discharge of complex industrial wastewater. The photocatalytic technology has been proved as an effective way to solve the problem, while an efficient photocatalyst is the most critical factor. Herein, a new photocatalyst MIL-68(Ga)_NH₂ was obtained by hydrothermal synthesis and were characterized by PXRD, FTIR, ¹H NMR, and TGA systematically. The result demonstrates that MIL-68(Ga)_NH₂ crystallized in orthorhombic system and Cmcm space group with the unit cell parameters: a = 36.699 Å, b = 21.223 Å, c = 6.75 Å, V = 5257.6 ų, which sheds light on the maintenance of the crystal structure of the prototype material after amino modification. The conversion of Cr(VI) and binary pollutant Cr(VI)/RhB in wastewater under visible light stimulation was characterized by the UV-vis DRS. Complementary experimental results indicate that MIL-68(Ga)_NH₂ exhibits remarkable photocatalytic activity for Cr(VI) and the degradation rate reaches as high as 98.5% when pH = 2 and ethanol as hole-trapping agent under visible light irradiation with good reusability and stability. Owing to the synergistic effect between Cr(VI) and RhB in the binary pollutant system, MIL-68(Ga)_NH₂ exhibits excellent catalytic activity for both the pollutants, the degradation efficiency of Cr(VI) and RhB was up to 95.7% and 94.6% under visible light irradiation for 120 min, respectively. The possible removal mechanism of Cr(VI)/RhB based on MIL-68(Ga)_NH₂ was explored. In addition, Ga-based MOF was applied in the field of photocatalytic treatment of wastewater for the first time, which broadened the application of MOF materials in the field of photocatalysis. Full article

To guarantee the security of new energy vehicles (NEV), which include energy storage devices such as batteries, a quartz crystal microbalance (QCM) sensor was designed to detect online the HF gas produced from the leakage of electrolyte in the power system. Based on the chemical properties of HF gas, an amino-functionalized metal–organic framework NH₂-MIL-101 (Cr) was synthesized as a sensing material of a QCM transducer to detect HF gas for NEV safeguard. The sensing materials are designed based on the hydrogen bond interaction between the amino group and HF molecular and were characterized by powder X-ray diffraction, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), etc. The performance of this sensor showed high sensitivity, with a limit of detection at 500 ppb, short response/recovery time and good reproducibility for anhydrous hydrogen fluoride (AHF) detection. Additionally, the sensing mechanism of NH₂-MIL-101(Cr) QCM resonator to AHF is revealed to be reversible chemical adsorption by Gaussian 09. It is well-matched with a result of experimental determination through temperature-varying microgravimetric experiments. Therefore, the amino-functionalized MIL-101(Cr) QCM resonator may be a good candidate for an NEV safety monitor due to its rapid response to HF leaked from the decomposition of the electrolyte. Full article

The laccase enzyme was successfully immobilized over a magnetic amino-functionalized metal–organic framework Fe₃O₄-NH₂@MIL-101(Cr). Different techniques were used for the characterization of the synthesized materials. The Fe₃O₄-NH₂@MIL-101(Cr) laccase showed excellent resistance to high temperatures and low pH levels with a high immobilization capacity and large activity recovery, due to the combination of covalent binding and adsorption advantages. The long-term storage of immobilized laccase for 28 days indicated a retention of 88% of its initial activity, due to the high stability of the immobilized system. Furthermore, a residual activity of 49% was observed at 85 °C. The immobilized laccase was effectively used for the biodegradation of Reactive Black 5 (RB) and Alizarin Red S (AR) dyes in water. The factors affecting the RB and AR degradation using the immobilized laccase (dye concentration, temperature and pH) were investigated to determine the optimum treatment conditions. The optimum conditions for dye removal were a 5 mg/L dye concentration, temperature of 25 °C, and a pH of 4. At the optimum conditions, the biodegradation and sorption-synergistic mechanism of the Fe₃O₄-NH₂@MIL-101(Cr) laccase system caused the total removal of AR and 81% of the RB. Interestingly, the reusability study of this immobilized enzyme up to five cycles indicated the ability to reuse it several times for water treatment. Full article

The presence of hexavalent chromium water pollution is a growing global concern. Among the currently applied technologies to remove Cr^VI, its adsorption and photocatalytic reduction to Cr^III less mobile and toxic forms are the most appealing because of their simplicity, reusability, and low energy consumption. However, little attention has been paid to bifunctional catalysts, that is, materials that can reduce Cr^VI to Cr^III and retain both hexavalent and trivalent chromium species at the same time. In this work, the dual Cr^VI adsorption–reduction capacity of two iconic photoactive water-stable zirconium and titanium-based metal–organic frameworks (MOFs) has been investigated: UiO-66-NH₂ and MIL-125. The bifunctionality of photoactive MOFs depends on different parameters, such as the particle size in MIL-125 or organic linker functionalization/defective positions in UiO-66 type sorbents. For instance, the presence of organic linker defects in UiO-66 has shown to be detrimental for the chromium photoreduction but beneficial for the retention of the Cr^III phototransformed species. Both compounds are able to retain from 90 to 98% of the initial chromium present at acidic solutions as well as immobilize the reduced Cr^III species, demonstrating the suitability of the materials for Cr^VI environmental remediation. In addition, it has been demonstrated that adsorption can be carried out also in a continuous flux mode through a diluted photoactive MOF/sand chromatographic column. The obtained results open the perspective to assess the bifunctional sorption and photoreduction ability of a plethora of MOF materials that have been applied for chromium capture and photoreduction purposes. In parallel, this work opens the perspective to develop specific chemical encoding strategies within MOFs to transfer this bifunctionality to other related water remediation applications. Full article

At present, the development of novel catalysts with high activity Selective Catalytic Reduction (SCR) reaction at the low temperature is still a challenge. In this work, the authors prepare CeO₂/quasi-MIL-101 catalysts with various amounts of deposited ceria by a double-solvent method, which are characterized by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and so on. The results show that the increase of Ce content has a great influence on the catalytic property of the catalyst. The introduction of Ce can promote the conversion between Cr³⁺ and Cr⁵⁺ and increase the proportion of lattice oxygen, which improves the activity of the catalyst. However, the catalyst will be peroxidized when the content of Ce is too high, resulting in the decline of the catalytic activity. This experiment indicates that CeO₂/quasi-MIL-101 plays a significant role in the NH₃-SCR process at the low temperature when the loading of Ce is 0.5%. This work has proved the potential of this kind of material in NH₃-SCR process at the low temperature, providing help for subsequent studies. Full article

Reversible structural transition between the Large (LP) and Narrow Pore (NP) forms (breathing phenomena) of the MIL-53(X, X = Al, Cr, Fe, Ga) Metal Organic Framework (MOF) is probably one of the most amazing physical properties of this class of soft-porous materials. Whereas great attention has been paid to the elucidation of the physical mechanism ruling this reversible transition, the effect of the functionalization on the flexibility has been less explored. Among functionalized MIL-53(Al) materials, the case of NH${}_2$-MIL-53(Al) is undoubtedly a very intriguing structural transition rarely observed, and the steadier phase corresponds to the narrow pore form. In this work, the flexibility of the NH${}_2$-MIL-53(Al) metal organic framework was investigated by means of molecular dynamics simulations. Guest (methanol) and thermal breathing of the NH${}_2$-MIL-53(Al) was thus explored. We show that it is possible to trigger a reversible transition between NP and LP forms upon adsorption, and we highlight the existence of stable intermediate forms and a very large pore phase. Furthermore, the NP form is found thermodynamically stable from 240 to 400 K, which is the result of strong intramolecular hydrogen bonds. Full article

This work proposes an efficient desulfurization system to produce low sulfur diesel under sustainable and moderate experimental conditions. Treatment of a real diesel with a sulfur content of 2300 ppm led to 80% desulfurization after 2 h. The processes used conciliate liquid-liquid extraction and sulfur oxidative catalysis. The catalytic performance of the commercial Keggin-polyoxomolybdate H₃[PMo₁₂O₄₀] (PMo₁₂) was strategically increased by simple cation exchange, using a long carbon chain (ODAPMo₁₂, ODA = CH₃(CH₂)₁₇(CH₃)₃N), and by its incorporation into the Metal-Organic Framework (MOF) NH₂-MIL-101(Cr), forming a new active heterogeneous PMo₁₂@MOF composite catalyst. Activity of both catalysts was similar; however, the solid catalyst could be easily recovered and reused, and its stability was confirmed after multiple continuous cycles. Full article