Aminated metal-organic framework (NH2-MIL-101(Cr)) incorporated polyvinylidene (PVDF) hybrid membranes: Synthesis and application in efficient removal of Congo red from aqueous solution

The efficient treatment of wastewater containing organic dyes generated in diverse industrial processes has become more crucial owing to increasing environmental concerns. In this paper, we incorporated the aminated functional NH₂-MIL-101(Cr) into the porous polyvinylidene fluoride (PVDF) to fabricate the MOFs/polymer hybrid membranes, which combined the surface activity of MOFs and the membrane's filtration plus the adsorption process, and can be used in the high-efficient removal of congo red (CR) from aqueous solution. Two synthesis strategies were employed, and both of which are useful in fabricating the NH₂-MIL-101(Cr)@PVDF hybrid membranes. The NH₂-MIL-101(Cr) particles are mainly incorporated into the pores of PVDF, and thus enhance the hydrophilicity, water flux as well as porosity of the hybrid membranes. In the adsorption experiments, the influences of various conditions including the solution pH, adsorption time, adsorption isotherms, reusability, and the filtration performances were investigated systematically, and all the hybrid membranes show evidently improved adsorption performances compared to original PVDF films. The adsorption thermal and dynamics analyses indicate that the adsorption process is mainly featured in Langmuir monolayer adsorption and chemical adsorption. The hydrogen bonding at the interface of CR/NH₂-MIL-101(Cr) is responsible for the selective adsorption of CR. The excellent reusability and the dynamic adsorption performances determine the potential applications of MOF-based hybrid membranes in the membrane separation of CR from practical waste water.     

Fluorescent MOF-based nanozymes for discrimination of phenylenediamine isomers and ratiometric sensing of o-phenylenediamine

Although peroxidase-like nanozymes have made great progress in bioanalysis,few current nanozymebased biosensors are constructed for discriminating isomers of organic compounds.Herein,fluorescent metal-organic framework（MOF）-based nanozyme is utilized for phenylenediamine isomers discrimination and detection.NH₂-MIL-101（Fe）,as a member of Fe-based MOFs,functions as not only fluorescent indicator but also peroxidase mimics.In the presence of H₂ O₂,NH2-MIL-101（Fe） c...     

A Humidity-Induced Large Electronic Conductivity Change of 107 on a Metal-Organic Framework for Highly Sensitive Water Detection

The electronic conductivity (EC) of metal–organic frameworks (MOFs) is sensitive to strongly oxidizing guest molecules. Water is a relatively mild species, however, the effect of H₂O on the EC of MOFs is rarely reported. We explored the effect of H₂O on the EC in the MOFs (NH₂)₂-MIL-125 and its derivatives with experimental and theoretical investigations. Unexpectedly, a large EC increase of 10⁷ on H₂SO₄@(NH₂)₂-MIL-125 by H₂O was observed. Brønsted acid–base pairs formed with the −NH₂ groups, and H₂SO₄ played an important role in promoting the charge transfer from H₂O to the MOF. Based on H₂SO₄@(NH₂)₂-MIL-125, a high-performance chemiresistive humidity sensor was developed with the highest sensitivity, broadest detection range, and lowest limit of detection amongst all reported sensing materials to date. This work not only demonstrated that H₂O can remarkably influence the EC of MOFs, but it also revealed that post-modification of the structure of MOFs could enhance the influence of the guest molecule on their EC to design high-performance sensing materials.     

Efficient and Sustainable in situ Photo-Fenton Reaction to Remove Phenolic Pollutants by NH2-MIL-101(Fe)/Ti3C2Tx Schottky-Heterojunctions

Metal-organic frameworks (MOFs) with abundant active sites, a class of materials composed of metal nodes and organic ligands, is widely used for photocatalytic degradation of pollutants. However, the rapid recombination of photoinduced carriers of MOFs limits its photocatalytic degradation performance. Herein, Ti₃C₂T_x nanosheets-based NH₂-MIL-101(Fe) hybrids with Schottky-heterojunctions were fabricated by in situ hydrothermal assembly for improved photocatalytic activity. The photodegradation efficiencies of the NH₂-MIL-101(Fe)/Ti₃C₂T_x (N-M/T) hybrids for phenol and chlorophenol were 96.36 % and 99.83 % within 60 minutes, respectively. The N-M/T Schottky-heterojunction duly transferred electrons to the Ti₃C₂T_x nanosheets surface via built-in electric fields, effectively suppressing the recombination of photogenerated carriers, thereby improving the photocatalytic performance of NH₂-MIL-101(Fe). Moreover, the Fe-mixed-valence in the N-M/T led to improvement in the efficiency of the in situ generated photo-Fenton reactions, further enhancing the photocatalytic activity with more generated reactive oxygen species (ROS). The study proposes a highly effective removal of phenolic pollutants in wastewater.     

Construction of NH2-MIL-125(Ti) nanoplates modified Bi2WO6 microspheres with boosted visible-light photocatalytic activity

Photoactive metal–organic frameworks (MOFs) have proven to be a promising porous material in the field of catalysis. Controllable integration of these MOFs with inorganic semiconductor materials may endow new multifunctional hybrid materials with preferable photocatalytic properties. In this research, NH₂-MIL-125(Ti) nanoplates modified Bi₂WO₆ microspheres was prepared via a simple solvothermal method. The photocatalytic behaviors of the acquired catalysts was evaluated via the degradation of tetracycline hydrochloride (TC) under visible light. The experimental results showed that NH₂-MIL-125(Ti)/Bi₂WO₆ composites display higher photocatalytic activity than that of single Bi₂WO₆, and the ideal incorporation amount of NH₂-MIL-125(Ti) was around 5 wt%. The steady state fluorescence spectrum, transient photocurrents and electrochemical impedance spectroscopy verified that the introduction of NH₂-MIL-125(Ti) could accelerate the separation and transfer of photogenerated carriers and thus improve the photocatalytic activity of Bi₂WO₆. The photocatalytic mechanism was explored in detail. This work extends the knowledge of integrating MOFs with traditional photocatalysts to form new composite materials in the area of environmental purification.

     

MIL-125(Ti)及其氨基功能化材料修饰石英晶体微天平的湿敏性能

采用简单的溶剂热法制备金属有机框架化合物MIL-125(Ti)和NH_2-MIL-125(Ti)材料,并通过X射线衍射仪、扫描电子显微镜、傅氏转换红外线光谱分析仪和比表面积测试仪对所得样品进行表征。将2种材料修饰构建为石英晶体微天平传感器,测试其在11%～97%RH相对湿度范围内的湿度感测性能。实验结果表明,基于MIL-125(Ti)和NH_2-MIL-125(Ti)构建的传感器对湿度具有灵敏度高、重复性好、响应/恢复快等特点。相对于没有氨基修饰的MIL-125(Ti),NH_2-MIL-125(Ti)材料修饰的传感器对湿度表现出更高的响应性能。在环境湿度约52%时,NH_2-MIL-125(Ti)传感器对11%RH湿度响应值比MIL-125(Ti)湿度传感器的大57 Hz,说明氨基功能化对MIL-125(Ti)的湿敏性能有显著的增强作用。此外,通过Materials Studio模拟计算获得了水分子与MIL-125(Ti)及NH_2-MIL-125(Ti)作用的吸附焓,也证明氨基功能化对MIL-125(Ti)的湿度敏感性能具有增强作用。     

Size- and Emission-Controlled Synthesis of Full-Color Luminescent Metal-Organic Frameworks for Tryptophan Detection

The development of nanoscaled luminescent metal–organic frameworks (nano-LMOFs) with organic linker-based emission to explore their applications in sensing, bioimaging and photocatalysis is of great interest as material size and emission wavelength both have remarkable influence on their performances. However, there is lack of platforms that can systematically tune the emission and size of nano-LMOFs with customized linker design. Herein two series of fcu - and csq -type nano-LMOFs, with precise size control in a broad range and emission colors from blue to near-infrared, were prepared using 2,1,3-benzothiadiazole and its derivative based ditopic- and tetratopic carboxylic acids as the emission sources. The modification of tetratopic carboxylic acids using OH and NH₂ as the substituent groups not only induces significant emission bathochromic shift of the resultant MOFs, but also endows interesting features for their potential applications. As one example, we show that the non-substituted and NH₂-substituted nano-LMOFs exhibit turn-off and turn-on responses for highly selective and sensitive detection of tryptophan over other nineteen natural amino acids. This work sheds light on the rational construction of nano-LMOFs with specific emission behaviours and sizes, which will undoubtedly facilitate their applications in related areas.     

CaO nanoparticles incorporated metal organic framework (NH2-MIL-101) for Knoevenagel condensation reaction

Porous materials based on NH₂-MIL-101(Cr) MOF and their hierarchical acid-base composite with non-precious CaO was successfully prepared using a one-pot scalable hydrothermal approach. The composites were characterized by XRD, FTIR, UV–vis, ¹HNMR, TGA, N₂ adsorption–desorption isotherms, HRTEM and FESEM. The quantitative assessment of the basic sites was performed by benzoic acid titration. The results reveal that there is no remarkable structural alterations in the NH₂-MIL-101(Cr) after incorporation of CaO. Raising the CaO content boosted the strength of and content of Lewis basic sites from 0.31 to 1.34 mmol g^?1 due to the incorporation with CaO (0.04). Knoevenagel condensation reactions were performed as the probe reactions over the CaO/NH₂-MIL-101(Cr) catalysts. Both basic and acidic sites potentially boosted the reaction. Pure NH₂-MIL-101(Cr) display the catalytic conversion in the reaction (11%) which could be attributed weak basic sites on the NH₂-MIL-101(Cr) framework. However, the conversion (%) was potentially increased over NH₂-MIL-101(Cr) loaded with various content of CaO. The highest performance of (99%) conversion was achieved for (0.04) CaO/NH₂-MIL-101(Cr) catalyst. Exceptional conversion above 90% have been obtained for benzaldehyde derivatives both withdrawing and donating electron moieties. The composites can be recycled in four runs with a very small loss in performance. Furthermore, the composites produced tend to be feasible for various catalytic processes, exploring new avenues to produce of novel inorganic and organic composite materials as heterogeneous catalysts.     

Accelerated FeIII/FeII redox cycle of Fenton reaction system using Pd/NH2-MIL-101(Cr) and hydrogen

In this paper, a novel improvement in the catalytic Fenton reaction system named MHACF-NH₂-MIL-101(Cr) was constructed based on H₂ and Pd/NH₂-MIL-101(Cr). The improved system would result in an accelerated reduction in Fe^III, and provide a continuous and fast degradation efficiency of the 10 mg L^-1 4-chlorophenol which was the model contaminant by using only trace level Fe^II. The activity of Pd/NH₂-MIL-101(Cr) decreased from 100% to about 35% gradually during the six consecutive reaction cycles of 18 h. That could be attributed to the irreversible structural damage of NH₂-MIL-101(Cr).     

An integrated supramolecular fungicide nanoplatform based on pH-sensitive metal–organic frameworks

The construction of an integrated nanoplatform with controlled fungicide delivery features in the specific microenvironment produced by fungal pathogens is a highly desirable strategy to improve the utilization of fungicides. Herein, we report a supramolecular fungicide delivery system based on benzimidazole-modified NH₂-MIL-101(Fe) metal–organic frameworks (B-MIL-101(Fe) MOFs) as carriers loaded with osthole (OS), and β-cyclodextrin (β-CD) as nanovalves to form β-CD@B-MIL-101(Fe)-OS. The nanoplatform can release the loaded OS for fungus control through self-degradation of the MOFs skeleton in an oxalic acid microenvironment produced by Botrytis cinerea. The experimental results exhibit that the constructed supramolecular fungicide delivery system could effectively inhibit mycelial growth and protect the tomatoes from infection by B. cinerea during the ripening stage. This strategy constructs a facile and integrated supramolecular drug delivery system for B. cinerea control and opens up a new avenue for the sustainable development of modern agriculture.     

Diimino Nickel Complex Anchored into the MOF Cavity as Catalyst for Epoxidation of Chalcones and Bischalcones

Nickel-pyridylimine complex was incorporated into (Cr)NH₂-MIL-101 through condensation of 2-pyridine carboxaldehyde and NiCl₂ in presence of (Cr)NH₂-MIL-101-MOF in a one pot method. The prepared catalyst was characterized by XRD, FTIR, SEM, TEM and NMR methods. The obtained catalyst demonstrates an appropriate pattern for a post-synthetic covalent modification with catalytic active sites. This heterogeneous catalyst showed efficiency in the epoxidation reaction of chalcones and bischalcones, and exhibited appropriate recyclability, rather short reaction times and high yields.     

Activated carbon/MOFs composite: AC/NH2-MIL-101(Cr), synthesis and application in high performance adsorption of p-nitrophenol

P-nitrophenol (PNP), a hazardous phenolic material, should be eliminated from water in order to prevent damage to the marine ecosystem, animals as well as humans. Although adsorption seems to become the most widely used strategy, an effective and strong-capacity adsorbent to minimize PNP under the approved concentration is essential to discovering. In this study, a class of porous adsorbents composite was developed for the PNP removal from water. AC-NH₂-MIL-101(Cr) has chosen to boost the removal of PNP from water owing to extremely porous and stable in water. The fabricated composite has 2049 m².g⁻¹ large surface area and 0.93 cm³.g⁻¹ pore volume. The adsorption kinetics and isotherms were investigated. AC-NH₂-MIL-101(Cr) was found to exhibit an adsorption capacity of ~ 18.3 mg g⁻¹. The mechanism for this strong adsorption performance was suggested and related to affinity NO₂ groups of PNP and the unsaturated chromium site of AC-NH₂-MIL-101(Cr), the coulombic interaction via the hydrogen bond between the PNP and AC-NH₂-MIL-101(Cr) and π-π stacking interaction. AC-NH₂-MIL-101(Cr) composite also displayed exceptional stability and reusability after a successive PNP removal processes. This study provides new insight into developing and synthesizing extremely effective nanoporous material for organic contaminants disinfection from waste water based on MOFs.     

Amine-Functionalized Metal–Organic Framework as a New Sorbent for Vortex-Assisted Dispersive Micro-Solid Phase Extraction of Phenol Residues in Water Samples Prior to HPLC Analysis: Experimental and Computational Studies

Metal–organic frameworks (MOFs) are a new class of hybrid inorganic–organic microporous crystalline materials, which possess unique properties such as high surface area, tunable pore size, and good thermal stability. These unique characteristics make MOFs interesting targets for sample pretreatment. In this work, MIL-53 material based on aluminum and containing amine functional groups (NH₂-MIL-53(Al)) was synthesized and applied as an efficient sorbent for development of vortex-assisted dispersive micro-solid phase extraction for eight United States Environmental Protection Agency’s priority phenols from aqueous samples prior to analysis by high-performance liquid chromatography with photodiode-array detection. A simple extraction process was designed. The parameters affecting the extraction efficiency, such as amount of sorbent, extraction time, type of desorption solvent and its volume were investigated. The good linearity in the concentration range of 0.0015–10.0000 μg mL^?1 with the coefficients of determination of greater than 0.9929, low limits of detection (0.0004–0.0133 μg mL^?1) and relative standard deviations of lower than 10% were obtained. The proposed method has been successfully applied to the determination of phenol compounds in different water sample matrices including treated water, waste water, river water, sea water, lake water, drinking water and tap water. In addition, computational simulation was performed to predict the adsorption ability of NH₂-MIL-53(Al) towards the studied phenolic compounds. The computational results were in agreement with the experimental studies and it has been proved that NH₂-MIL-53(Al) is promising for enrichment of phenolic pollutants.     

Reverse Replacement in NH2-MIL-125 with 1,4-Dicarboxybenzene for Enhanced Photocatalytic Hydrogen Generation

Metal-organic frameworks (MOFs) constructed by ligands and metal clusters, have been considered as a promising material for photocatalytic water splitting. In this work, a solvent-assisted ligand exchange (SALE) method has been applied through partial reverse substitution of the ligand in NH₂-MIL-125 (Ti) by 1,4-dicarboxybenzene (BDC). This modification strategy can optimize the charge transfer dynamics together with the preserved light absorption, resulting in a 3.3 times higher hydrogen production rate compared to the pristine material under visible-light irradiation. This work broadens the field of ligand modifications of MOFs to boost the photocatalytic performance.     

Photocatalytic Activities of FeNbO4/NH2-MIL-125(Ti) Composites toward the Cycloaddition of CO2 to Propylene Oxide

Photocatalytic utilization of CO₂ in the production of value-added chemicals has presented a recent green alternative for CO₂ fixation. In this regard, three FeNbO₄/NH₂-MIL-125(Ti) composites of different mole ratios were synthesized, characterized using Powder X-ray diffraction (PXRD), UV–vis diffuse reflectance spectroscopy (UV-Vis DRS), Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX). PXRD patterns confirm the co-existence of the parent components in the prepared composites. Moreover, the surface area increased as the mole percent of NH₂-MIL-125(Ti) in the composites increased due to the large surface area of NH₂-MIL-125(Ti). Prepared composites were investigated for the photocatalytic insertion of CO₂ into propylene oxide. FeNbO_4(75%)/NH₂-MIL-125(Ti)_(25%) showed the highest percent yield of 52% compared to the other two composites. Results demonstrate the cooperative mechanism between FeNbO₄ and NH₂-MIL-125(Ti) and that the reaction proceeded photocatalytically.     

Evaluation of UiO‐66 metal organic framework as an effective sorbent for Curcumin's overdose

Metal organic frameworks (MOFs) UiO‐66 (UiO stands for University of Oslo) and NH₂‐UiO‐66 were prepared and characterized as sorbent (antidotal agents) for curcumin (CUR) adsorption. The structure of products were characterized by X‐ray powder diffraction (XRD), Field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Attenuated Total Reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), and N₂ adsorption–desorption measurements. FESEM showed NH₂‐UiO‐66 displayed symmetrical crystals with triangular base pyramid morphology, with the particle size around 100 nm and uniform size distribution. Adsorption capacities of CUR/MOFs with different mass ratios in the feed were investigated in the present study, and this investigation revealed that when the CUR/MOFs with mass ratio was around 0.4, the absorption capacity of NH₂‐UiO‐66 had tended to maximum. Although, functionalization reduced the specific surface area and free volume, introducing polar amine groups could improve the affinity of NH₂‐UiO‐66 respect to CUR. Kinetic studies showed that the kinetic data are well fitted with the pseudo‐ second‐order model. MTT assay revealed that MOFs at the concentration range of 0–560 μg/ml had no cytotoxic effect on the Human Foreskin Fibroblast normal cell line (HFF‐2). These results suggest that these MOFs could be safe as sorbent for adsorb CUR from the body.     

pH and thermo responsive aliphatic tertiary amine chromophore hyperbranched poly(amino ether ester)s from oxa-Michael addition polymerization

In this research, we developed a novel and facile strategy to prepare aliphatic tertiary amine chromophore hyperbranched poly(amino ether ester)s with pH and thermo responsiveness via phosphazene base (t-BuP₂) catalyzed oxa-Michael addition polymerization of triethanolamine with ethylene glycol diacrylate at room temperature. UV–vis and fluorescence analyses results showed that the tertiary amine at branching point for hyperbranched poly(amino ether ester)s is very important to retain strong blue fluorescence of tertiary amine chromophore. Moreover, the hyperbranched poly(amino ether ester)s exhibit an aggregation caused quenching (ACQ) fluorescence, solvent induced red-shifted emission, molecular weight, and temperature dependent emission characters. More interestingly, the hyperbranched poly(amino ether ester)s show extreme acid induced quenching fluorescence phenomenon, and also display good water solubility, specific recognition of Fe³⁺ ion, low cytotoxicity, and bright cell imaging, which could serve as a microenvironment-responding fluorescent probe for application in chemical sensing, cell imaging, drug delivery, or disease diagnostics. This research provides a versatile method for the preparation of stimuli-responsive aliphatic tertiary amine chromophore polymers, and supplies ideas for researchers to explore other unconventional fluorescent polymers for application.     

Metal-organic framework functionalized with deep eutectic solvent for solid-phase extraction of Rhodamine 6G in water and cosmetic products

An NH₂-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was synthesized for extraction and determination of Rhodamine (Rh) 6G from environmental and cosmetic samples. The deep eutectic solvent (DES) was prepared by mixing choline chloride and urea in a mole ratio of 1:2. NH₂-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was synthesized using the impregnation method at a ratio of 60:40 (w/w). The optimum conditions were determined after NH₂-MIL-53(Al)-DES(ChCl-Urea) characterization was performed. The optimum conditions were determined as pH 8, adsorbent amount of 15 mg, total adsorption-desorption time of 6 min, and enrichment factor of 20. The recovery values of the solid-phase extraction method for water and cosmetic samples under optimum conditions were between 95% and 106%. NH₂-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was an economically advantageous adsorbent because of its reusability of 15 times. All analyses were performed using the ultraviolet-visible spectrophotometer. The linear range, limit of detection, and limit of quantification of the method were 100–1000, 9.80, and 32.68 μg/L, respectively. The obtained results showed that the synthesized nanocomposite is a suitable adsorbent for the determination of Rh 6G in water and cosmetic samples. The real sample applications were verified with the high-performance liquid chromatography system.     

Long‐Term Photostability in Terephthalate Metal–Organic Frameworks

Prolonged (weeks) UV/Vis irradiation under Ar of UiO‐66(Zr), UiO66 Zr‐NO₂, MIL101 Fe, MIL125 Ti‐NH₂, MIL101 Cr and MIL101 Cr(Pt) shows that these MOFs undergo photodecarboxylation of benzenedicarboxylate (BDC) linker in a significant percentage depending on the structure and composition of the material. Routine characterization techniques such as XRD, UV/Vis spectroscopy and TGA fail to detect changes in the material, although porosity and surface area change upon irradiation of powders. In contrast to BCD‐containing MOFs, zeolitic imidazolate ZIF‐8 does not evolve CO₂ or any other gas upon irradiation.     

Water Stable Zr–Benzenedicarboxylate Metal–Organic Frameworks as Photocatalysts for Hydrogen Generation

The Zr‐containing metal–organic frameworks (MOFs) formed by terephthalate (UiO‐66) and 2‐aminoterephthalate ligands [UiO‐66(NH₂)] are two notably water‐resistant MOFs that exhibit photocatalytic activity for hydrogen generation in methanol or water/methanol upon irradiation at wavelength longer than 300 nm. The apparent quantum yield for H₂ generation using monochromatic light at 370 nm in water/methanol 3:1 was of 3.5 % for UiO‐66(NH₂). Laser‐flash photolysis has allowed detecting for UiO‐66 and UiO‐66(NH₂) the photochemical generation of a long lived charge separated state whose decay is not complete 300 μs after the laser flash. Our finding and particularly the influence of the amino group producing a bathochromic shift in the optical spectrum without altering the photochemistry shows promises for the development of more efficient MOFs for water splitting.