Optimized Sieving Effect for Ethanol/Water Separation by Ultramicroporous MOFs

A Highly Chemically Robust 3D Interpenetrated MOF Heterogeneous Catalyst for the Synthesis of Hantzsch 1,4-Dihydropyridines and Drug Molecules

Metal-organic frameworks (MOFs) have attracted immense attention as efficient heterogeneous catalysts over other solid catalysts, however, their chemical environment instability often limits their catalytic potential. Herein, utilizing a flexible unexplored tetra-acid ligand and employing the mixed ligand approach, a 3D interpenetrated robust framework is strategically developed, IITKGP-51 (IITKGP stands for Indian Institute of Technology Kharagpur), which retained its crystallinity over a wide range of pH solution (4-12). Having ample open metal sites (OMSs), IITKGP-51 is explored as a heterogeneous catalyst in one-pot Hantzsch condensation reaction, with low catalyst loading for a broad range of substrates. The synthesis of drug molecules remains one of the most significant and emergent areas of organic and medicinal chemistry. Considering such practical utility, biologically important Nemadipine B and Nifedipine drug molecules (calcium channel protein inhibitor) are synthesized for the first time by using this catalyst and fully characterized via SC-XRD and other spectroscopic methods. This report inaugurates the usage of a MOF material as a catalyst for the synthesis of drug molecules.

Improving the removal efficiency of oxygenated volatile organic compounds by defective UiO-66 regulated with water

The purification of oxygenated volatile organic compounds VOCs (OVOCs), important precursors of ozone and particulate matters, has triggered intensive research interests. UiO-66 with high photocatalytic activity have shown great potential. However, the lack of active sites severely limited the trapping and degradation of OVOCs. Herein, reo-UiO-66 with increased specific surface area, hierarchical porous structure and tunable acidic/basic sites was synthesized by simply adding water as the modulator. XRD, TGA and FTIR results confirmed the formation of reo-defects, which significantly affected the surface hydrophilicity and active sites of UiO-66. The adsorption of Lewis acidic acetaldehyde was enhanced by 265 times with coordinative unsaturated Zr acting as the dominant adsorption sites. The degradation efficiency of typical OVOCs (acetaldehyde and acetone) increased from 0% and 25% to 50% and 73%, respectively. This work provided a facile method to modulate the micro-environment in MOFs for the efficient capture and catalytic purification of OVOCs.

A microporous bismuth-based MOF for efficient separation of acetylene from carbon dioxide

The separation of acetylene from carbon dioxide is challenging due to their almost identical molecular sizes and volatilities. Metal-organic frameworks (MOFs) in general are strong candidates for the separation of gas mixtures owing to the presence of functional pore surfaces that can selectively capture specific target molecules. Herein, we report a stable and easily synthesized bismuth-based MOF, Bi-BTC, which can achieve the separation of acetylene and carbon dioxide. We performed a detailed analysis of the sorption properties of the Bi-MOF. Bi-BTC shows good adsorption capacities for C2H2 with a capacity of 53.8 cm3 g-1 at 298 K and 1.0 bar, and C2H2/CO2 selectivity of 5.14/7.69 at 298 K and 1.0/0.1 bar. IAST selectivity calculations indicate that Bi-BTC possesses good separation capacity, and dynamic breakthrough experiments were performed to prove the separation of C2H2 and CO2. Bi-MOFs as a group of relatively less studied types of MOFs have interesting adsorption characteristics, and this study on Bi-based MOF will enrich three-dimensional Bi-MOF adsorbents for gas adsorption and separation applications.

Sulfonated vitamin K3 mediated bimetallic metal-organic framework for multistage augmented cancer therapy

Chemodynamic therapy (CDT) relying on Fenton reaction has emerged as a promising strategy for tumor treatment. However, its clinical efficacy is hindered by the inadequate reactive oxygen species (ROS) and the potential cytotoxicity towards normal cells. To address these challenges, we have successfully developed a multistage augmented cancer therapy system based on bimetallic metal-organic framework (BMOF) that amplifies ROS and facilitates tumor-specific therapeutic effects. By employing a simple one-pot self-assembly approach, we synthesized SVK3@ZnCo-ZIF in which sulfonated vitamin K3 (SVK3) was encapsulated within ZnCo-ZIF BMOF. The results revealed that the incorporation of Zn atoms significantly diluted the Fenton activity of Co atoms towards normal cells. Notably, SVK3@ZnCo-ZIF underwent pH-controlled decomposition triggered by the tumor microenvironment (TME), thus releasing SVK3, Co2+ and Zn2+. Specifically, the H2O2 levels in tumors was effectively elevated by the interaction of SVK3 with NAD(P)H quinone oxidoreductase-1 (NQO-1). It thus enhanced the Fenton activity of Co2+. Moreover, the release of Zn2+ ions can induce cellular dysfunction and mitochondrial damage, thereby promoting the generation of ROS and subsequent cell death. The synergistic combination of CDT, SVK3 chemotherapy, and Zn2+-interfered therapy greatly facilitated apoptosis of tumor cells. Collectively, our investigations demonstrate the efficacy of such system in selectively inducing toxicity in cancer cells while minimizing detrimental effects on normal cells.

Optimizing Sieving Effect for CO2 Capture from Humid Air Using an Adaptive Ultramicroporous Framework

Excessive CO2 in the air can not only lead to serious climate problems but also cause serious damage to humans in confined spaces. Here, a novel metal-organic framework (FJI-H38) with adaptive ultramicropores and multiple active sites is prepared. It can sieve CO2 from air with the very high adsorption capacity/selectivity but the lowest adsorption enthalpy among the reported physical adsorbents. Such excellent adsorption performances can be retained even at high humidity. Mechanistic studies show that the polar ultramicropore is very suitable for molecular sieving of CO2 from N2 , and the distinguishable adsorption sites for H2 O and CO2 enable them to be co-adsorbed. Notably, the adsorbed-CO2 -driven pore shrinkage can further promote CO2 capture while the adsorbed-H2 O-induced phase transitions in turn inhibit H2 O adsorption. Moreover, FJI-H38 has excellent stability and recyclability and can be synthesized on a large scale, making it a practical trace CO2 adsorbent. This will provide a new strategy for developing practical adsorbents for CO2 capture from the air.

Ultra-Microporous and Stable MOFs with Zero-Linker Ligands for Gas Capture and Separation

Zero-linker ligands have maximized the size coordination efficiency of the metal ions in MOF framework which is important in constructing ultra-microporous MOFs with high stability and density, a bridge between zeolites and traditional MOFs. This article highlighted several recently developed ultra-microporous MOFs with zero-linker ligands for gas capture and separation.

Fast Water Transport in UTSA-280 via a Knock-Off Mechanism

Water and other small molecules frequently coordinate within metal-organic frameworks (MOFs). These coordinated molecules may actively engage in mass transfer, moving together with the transport molecules, but this phenomenon has yet to be examined. In this study, we explore a unique water transfer mechanism in UTSA-280, where an incoming water molecule can displace a coordinated molecule for mass transfer. We refer to this process as the "knock-off" mechanism. Despite UTSA-280 possessing one-dimensional channels, the knock-off transport enables water movement along the other two axes, effectively simulating a pseudo-three-dimensional mass transfer. Even with a relatively narrow pore width, the knock-off mechanism enables a high water flux in the UTSA-280 membrane. The knock-off mechanism also renders UTSA-280 superior water/ethanol diffusion selectivity for pervaporation. To validate this unique mechanism, we conducted 1 H and 2 H solid-state NMR on UTSA-280 after the adsorption of deuterated water. We also derived potential energy diagrams from the density functional theory to gain atomic-level insight into the knock-off and the direct-hopping mechanisms. The simulation findings reveal that the energy barrier of the knock-off mechanism is marginally lower than the direct-hopping pathway, implying its potential role in enhancing water diffusion in UTSA-280.

Highly Robust Metal-Organic Framework for Efficiently Catalyzing Knoevenagel Condensation and the Strecker Reaction under Solvent-Free Conditions

Metal-organic frameworks (MOFs) have been recognized as one of the most promising porous materials and offer great opportunities for the rational design of new catalytic solids having great structural diversity and functional tunability. Despite numerous inherent merits, their chemical environment instability limits their practical usage and demands further exploration. Herein, by employing the mixed-ligand approach, we have designed and developed a robust 3D Co-MOF, [Co2(μ2-O)(TDC)2(L)(H2O)2]·2DMF (H2TDC = 2,5-thiophenedicarboxylic acid, L = 3,3'-azobispyridine), IITKGP-50 (IITKGP stands for the Indian Institute of Technology Kharagpur), which exhibited excellent framework robustness not only in water but also in a wide range of aqueous pH solutions (pH = 2-12). Taking advantage of superior framework robustness and the presence of high-density open metal sites, IITKGP-50 was further explored in catalyzing the two-component Knoevenagel condensation reaction and three-component Strecker reactions. Moreover, to verify the size selectivity of IITKGP-50, smaller to bulkier substrates in comparison with the MOF's pore cavity (8.1 × 5.6 Å2) were employed, in which relatively lesser conversions for the sterically bulkier aldehyde derivatives confirmed that the catalytic cycle occurs inside the pore cavity. The easy scalability, lower catalyst loading compared to that of benchmark MOFs, magnificent conversion rate over a wide range of substrates, and excellent recyclability without significant performance loss made IITKGP-50 a promising heterogeneous catalyst candidate.

Hierarchical Mesoporous Metal-Organic Frameworks with Boric Acid Sites on the Inner Surface of Small Mesopores for the Extraction of Nucleotides in Human Plasma Samples

In this work, a boronate affinity-functionalized hierarchical mesoporous metal-organic framework adsorbent with boronate sites only in the small mesopore has been structured based on UiO-66@Fe₃O₄. The introduction of large mesopores in the adsorbent can promote the diffusion of small cis-diol-containing compounds (cis-diols) into small mesopore channels, and the removal of the adsorption sites on the external surface of materials and in large mesopores can enhance the size-exclusion effect of the adsorbent. In addition, the adsorbent has faster adsorption kinetics and excellent selectivity to small cis-diols. Finally, a magnetic dispersive solid-phase extraction coupled with high-performance liquid chromatography was established for the enrichment and detection of nucleotides in plasma. Four nucleotides achieve the recoveries from 93.25 to 118.79%, the limits of detection from 0.35 to 1.26 ng·mL^-1, and the intra-day and inter-day relative standard deviations of less than 10.2%. In conclusion, this method can be directly used for the detection of small cis-diol targets in complex biological samples without protein precipitation prior to the extraction.