Amine-Rich Porous MOF Nanocrystals for the Selective Capture of Carcinogenic Anions and Organo-Pollutants from the Waste Water Environment at Neutral pH

The escalating concentration of hazardous Cr(VI) and pharmaceutical waste in water bodies underscores the imperative need to advance sustainable, cost-effective, and recyclable technologies to eliminate these pollutants from wastewater, thereby ensuring the safety and purity of drinking water supply. We have constructed an amine-rich, highly robust, reusable, porous three-dimensional nanosized (15–35 nm) Zr(IV) metal–organic framework (1′) for selective and eco-friendly removal of lethal Cr(VI) oxo-anions and pharmaceutical waste (i.e., ibuprofen) from the aqueous medium at neutral pH (pH 7). 1′ exhibits a highly positive charged surface, entraps toxic anionic Cr(VI) oxo-anion pollutants over its surface in a reversible manner, and converts them into less toxic Cr(III) species, within less than 30 s. The equilibrium adsorption capacities (qe) of 1′ for CrO42–, Cr2O72–, and ibuprofen were 223.4, 146.6, and 323.3 mg/g (according to Langmuir fitting), respectively, which are among the highest sorption capacities achieved by MOF adsorbents. With faster adsorption kinetics, 1′ showed a negligible effect in adsorption performance even in the coexistence of 50 times excess concentration of other possible anionic species. Further, the potential removal of CrO42–, Cr2O72–, and ibuprofen from complicated environmental water samples was executed by 1′ with negligible change in efficiency. Furthermore, an ion exchange silica-based reusable column was constructed with a 1% loading of 1′ for efficient and rapid removal of oxo-anions on a larger scale. The ion exchange column efficiently removes Cr(VI) oxo-anions and enables us to lower the concentration of Cr(VI) in drinking water to levels below the prescribed threshold (100 ppb, as per US-EPA recommendation). In addition, the probable mechanisms behind the adsorption-based removal of Cr(VI) oxo-anions and the organic pollutant ibuprofen by cationic 1′ were systematically inspected through various instrumental techniques

Amine-Rich Porous MOF Nanocrystals for the Selective Capture of Carcinogenic Anions and Organo-Pollutants from the Waste Water Environment at Neutral pH

The escalating concentration of hazardous Cr(VI) and pharmaceutical waste in water bodies underscores the imperative need to advance sustainable, cost-effective, and recyclable technologies to eliminate these pollutants from wastewater, thereby ensuring the safety and purity of drinking water supply. We have constructed an amine-rich, highly robust, reusable, porous three-dimensional nanosized (15–35 nm) Zr(IV) metal–organic framework (1′) for selective and eco-friendly removal of lethal Cr(VI) oxo-anions and pharmaceutical waste (i.e., ibuprofen) from the aqueous medium at neutral pH (pH 7). 1′ exhibits a highly positive charged surface, entraps toxic anionic Cr(VI) oxo-anion pollutants over its surface in a reversible manner, and converts them into less toxic Cr(III) species, within less than 30 s. The equilibrium adsorption capacities (qe) of 1′ for CrO42–, Cr2O72–, and ibuprofen were 223.4, 146.6, and 323.3 mg/g (according to Langmuir fitting), respectively, which are among the highest sorption capacities achieved by MOF adsorbents. With faster adsorption kinetics, 1′ showed a negligible effect in adsorption performance even in the coexistence of 50 times excess concentration of other possible anionic species. Further, the potential removal of CrO42–, Cr2O72–, and ibuprofen from complicated environmental water samples was executed by 1′ with negligible change in efficiency. Furthermore, an ion exchange silica-based reusable column was constructed with a 1% loading of 1′ for efficient and rapid removal of oxo-anions on a larger scale. The ion exchange column efficiently removes Cr(VI) oxo-anions and enables us to lower the concentration of Cr(VI) in drinking water to levels below the prescribed threshold (100 ppb, as per US-EPA recommendation). In addition, the probable mechanisms behind the adsorption-based removal of Cr(VI) oxo-anions and the organic pollutant ibuprofen by cationic 1′ were systematically inspected through various instrumental techniques

Amine-Rich Porous MOF Nanocrystals for the Selective Capture of Carcinogenic Anions and Organo-Pollutants from the Waste Water Environment at Neutral pH

The escalating concentration of hazardous Cr(VI) and pharmaceutical waste in water bodies underscores the imperative need to advance sustainable, cost-effective, and recyclable technologies to eliminate these pollutants from wastewater, thereby ensuring the safety and purity of drinking water supply. We have constructed an amine-rich, highly robust, reusable, porous three-dimensional nanosized (15–35 nm) Zr(IV) metal–organic framework (1′) for selective and eco-friendly removal of lethal Cr(VI) oxo-anions and pharmaceutical waste (i.e., ibuprofen) from the aqueous medium at neutral pH (pH 7). 1′ exhibits a highly positive charged surface, entraps toxic anionic Cr(VI) oxo-anion pollutants over its surface in a reversible manner, and converts them into less toxic Cr(III) species, within less than 30 s. The equilibrium adsorption capacities (qe) of 1′ for CrO42–, Cr2O72–, and ibuprofen were 223.4, 146.6, and 323.3 mg/g (according to Langmuir fitting), respectively, which are among the highest sorption capacities achieved by MOF adsorbents. With faster adsorption kinetics, 1′ showed a negligible effect in adsorption performance even in the coexistence of 50 times excess concentration of other possible anionic species. Further, the potential removal of CrO42–, Cr2O72–, and ibuprofen from complicated environmental water samples was executed by 1′ with negligible change in efficiency. Furthermore, an ion exchange silica-based reusable column was constructed with a 1% loading of 1′ for efficient and rapid removal of oxo-anions on a larger scale. The ion exchange column efficiently removes Cr(VI) oxo-anions and enables us to lower the concentration of Cr(VI) in drinking water to levels below the prescribed threshold (100 ppb, as per US-EPA recommendation). In addition, the probable mechanisms behind the adsorption-based removal of Cr(VI) oxo-anions and the organic pollutant ibuprofen by cationic 1′ were systematically inspected through various instrumental techniques

3D Luminescent Amide-Functionalized Cadmium Tetrazolate Framework for Selective Detection of 2,4,6-Trinitrophenol

A new 3D fluorescent amide-functionalized Cd­(II)-based metal–organic framework (MOF) with molecular formula [Cd₅Cl₆(<b>L</b>)­(H<b>L</b>)₂]·7H₂O (<b>1</b>) was synthesized under solvothermal conditions using CdCl₂·H₂O and 4-(1<i>H</i>-tetrazol-5-yl)-<i>N</i>-[4-(1<i>H</i>-tetrazol-5-yl)­phenyl]­benzamide (H₂<b>L</b>) in DMF/methanol in the presence of conc. HCl. Single-crystal X-diffraction analysis reveals that the 3D framework structure of <b>1</b> is constructed from octahedrally coordinated Cd²⁺ ions interconncted by chloride anions and ditopic tetrazolate-based ligand molecules. The phase-purity of the compound was confirmed by X-ray powder diffraction (XRPD) analysis, infrared spectroscopy, and elemental analysis. Thermogravimetric analysis suggests that <b>1</b> is thermally stable up to 300 °C. Steady-state fluorescence titration experiments reveal that activated <b>1</b>′ can selectively detect 2,4,6-trinitrophenol (TNP) in the presence of other competing nitroaromatic compounds with a detection limit of 42.84 ppb. Recyclability experiments reveal that <b>1</b>′ retains its initial fluorescence intensity even after several cycles, suggesting high photostability and reusability for long-term sensing applications. The extraordinarily selective fluorescence quenching is assigned to the presence of energy and electron transfer processes as well as the electrostatic interactions of the MOF with TNP. This new 3D amide-functionalized MOF is a potential candidate that can be developed into a highly selective and sensitive sensing device for the in-field detection of TNP

Selective Sensing of Peroxynitrite by Hf-Based UiO-66-B(OH)₂ Metal–Organic Framework: Applicability to Cell Imaging

The first boronic acid functionalized Hf-based UiO-66 (UiO = University of Oslo) metal–organic framework (MOF) having the ability to detect both extracellular and intracellular peroxynitrite is presented. The Hf-UiO-66-B­(OH)₂ material (<b>1</b>) was synthesized under solvothermal conditions from a mixture of HfCl₄ and 2-borono-1,4-benzenedicarboxylic acid [H₂BDC–B­(OH)₂] ligand in DMF in the presence of formic acid (modulator) at 130 °C for 48 h. The desolvated material (<b>1′</b>) was utilized as a fluorescent turn-on probe for the rapid sensing of extracellular peroxynitrite (ONOO^–) under conditions mimicking those of biological medium (10 mM HEPES buffer, pH 7.4). Selective sensing of ONOO^– over other ROS/RNS was also achieved by <b>1′</b>. The oxidative cleavage of attached boronic acid groups forming corresponding hydroxy-functionalized ligands can be accounted for the fluorescent increment phenomenon in the presence of ONOO^–. The probe showed extraordinary sensitivity (detection limit = 9.0 nM) toward ONOO^– in 10 mM HEPES buffer at pH 7.4. Probe-loaded cells did not exhibit cytotoxicity and morphological deformities. It is remarkable that the probe inside the cells responded toward the peroxynitrite solution to give an intense blue fluorescent signal. The fluorescence microscopy study with J774A.1 macrophage cells unambiguously demonstrated that probe <b>1′</b> is suitable to image peroxynitrite in living cells

New Functionalized Metal–Organic Frameworks MIL-47‑X (X = −Cl, −Br, −CH₃, −CF₃, −OH, −OCH₃): Synthesis, Characterization, and CO₂ Adsorption Properties

Six new functionalized vanadium hydroxo terephthalates [V^III(OH)­(BDC-X)]·n­(guests) (MIL-47­(V^III)-X-AS) (BDC = 1,4-benzene­di­carboxylate; X = −Cl, −Br, −CH₃, −CF₃, −OH, −OCH₃; AS = as-synthesized) along with the parent MIL-47 were synthesized under rapid microwave-assisted hydrothermal conditions (170 °C, 30 min, 150 W). The unreacted H₂BDC-X and/or occluded solvent molecules can be removed by thermal activation under vacuum, leading to the empty-pore forms of the title compounds (MIL-47­(V^IV)-X). Except pristine MIL-47 (+III oxidation state), the vanadium atoms in all the evacuated functionalized solids stayed in the +IV oxidation state. The phase purity of the compounds was ascertained by X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, Raman, thermogravimetric (TG), and elemental analysis. The structural similarity of the filled and empty-pore forms of the functionalized compounds with the respective forms of parent MIL-47 was verified by cell parameter determination from XRPD data. TGA and temperature-dependent XRPD (TDXRPD) experiments in an air atmosphere indicate high thermal stability in the 330–385 °C range. All the thermally activated compounds exhibit significant microporosity (<i>S</i>_BET in the 305–897 m² g^–1 range), as verified by the N₂ and CO₂ sorption analysis. Among the six functionalized compounds, MIL-47­(V^IV)-OCH₃ shows the highest CO₂ uptake, demonstrating the determining role of functional groups on the CO₂ sorption behavior. For this compound and pristine MIL-47­(V^IV), Widom particle insertion simulations were performed based on ab initio calculated crystal structures. The theoretical Henry coefficients show a good agreement with the experimental values, and calculated isosurfaces for the local excess chemical potential indicate the enhanced CO₂ affinity is due to two effects: (i) the interaction between the methoxy group and CO₂ and (ii) the collapse of the MIL-47­(V^IV)-OCH₃ framework

New V^IV-Based Metal–Organic Framework Having Framework Flexibility and High CO₂ Adsorption Capacity

A vanadium based metal–organic framework (MOF), VO­(BPDC) (BPDC^2– = biphenyl-4,4′-dicarboxylate), adopting an expanded MIL-47 structure type, has been synthesized via solvothermal and microwave methods. Its structural and gas/vapor sorption properties have been studied. This compound displays a distinct breathing effect toward certain adsorptives at workable temperatures. The sorption isotherms of CO₂ and CH₄ indicate a different sorption behavior at specific temperatures. In situ synchrotron X-ray powder diffraction measurements and molecular simulations have been utilized to characterize the structural transition. The experimental measurements clearly suggest the existence of both narrow pore and large pore forms. A free energy profile along the pore angle was computationally determined for the empty host framework. Apart from a regular large pore and a regular narrow pore form, an overstretched narrow pore form has also been found. Additionally, a variety of spectroscopic techniques combined with N₂ adsorption/desorption isotherms measured at 77 K demonstrate that the existence of the mixed oxidation states V^III/V^IV in the titled MOF structure compared to pure V^IV increases the difficulty in triggering the flexibility of the framework

<i>p</i>-Xylene-Selective Metal–Organic Frameworks: A Case of Topology-Directed Selectivity

Para-disubstituted alkylaromatics such as <i>p</i>-xylene are preferentially adsorbed from an isomer mixture on three isostructural metal–organic frameworks: MIL-125(Ti) ([Ti₈O₈(OH)₄(BDC)₆]), MIL-125(Ti)-NH₂ ([Ti₈O₈(OH)₄(BDC-NH₂)₆]), and CAU-1(Al)-NH₂ ([Al₈(OH)₄(OCH₃)₈(BDC-NH₂)₆]) (BDC = 1,4-benzenedicarboxylate). Their unique structure contains octahedral cages, which can separate molecules on the basis of differences in packing and interaction with the pore walls, as well as smaller tetrahedral cages, which are capable of separating molecules by molecular sieving. These experimental data are in line with predictions by molecular simulations. Additional adsorption and microcalorimetric experiments provide insight in the complementary role of the two cage types in providing the para selectivity