Bioinspired nickel phosphide electrocatalysts achieve breakthrough efficiency and selectivity for C3 and C4 products.

This review illustrates molecular-scale confinement, containment, isolation, and related concepts to present MOF-centric catalysts and to realize desired chemical transformations.

Metal–organic frameworks are versatile materials that provide new opportunities as catalysts in polymerization reactions, including modularity and well-defined structures.

While linkers with various conformations pose challenges in the design and prediction of metal–organic framework (MOF) structures, they ultimately provide great opportunities for the discovery of novel structures thereby enriching structural diversity. Tetratopic carboxylate linkers, for example, have been widely used in the formation of Zr-based MOFs due to the ability to target diverse topologies, providing a promising platform to explore their mechanisms of formation. However, it remains a challenge to control the resulting structures when considering the complex assembly of linkers with unpredicted conformations and diverse Zr6 node connectivities. Herein, we systematically explore how solvents and modulators employed during synthesis influence the resulting topologies of Zr-MOFs, choosing H4TCPB-Br2 (1,4-dibromo-2,3,5,6-tetrakis­(4-carboxyphenyl)­benzene) as a representative tetratopic carboxylate linker. By modulating the reaction conditions, the conformations of the linker and the connectivities of the Zr6 node can be simultaneously tuned, resulting in four types of structures: a new topology (NU-500), she (NU-600), scu (NU-906), and csq (NU-1008). Importantly, we have synthesized the first 5-connected Zr6 node to date with the (4,4,4,5)-connected framework, NU-500. We subsequently performed detailed structural analyses to uncover the relationship between the structures and topologies of these MOFs and demonstrated the crucial role that the flexible linker played to access varied structures by different degrees of linker deformation. Due to a variety of pore structures ranging from micropores to hierarchical micropores and mesopores, the resulting MOFs show drastically different behaviors for the adsorption of n-hexane and dynamic adsorption of 2-chloroethyl ethyl sulfide (CEES) under dry and humid conditions.

A chemically and thermally stable, mesoporous, crystalline metal–organic framework, NU-1000, serves as a structurally well-defined support for catalytic reactions. Depositing chromium­(III), a metal widely used in homogeneous ethylene oligomerization catalysts, onto the Zr6 node of NU-1000 allows for the atomically precise determination of the structure of the Cr3+ catalyst through single-crystal X-ray diffraction studies. Chromium modification of NU-1000 was accomplished via solvothermal deposition in MOFs (SIM); termed Cr-SIM-NU-1000, the elaborated material features individual Cr atoms directed in single-site fashion into the mesopore of NU-1000. It was found that NU-1000 serves to stabilize the catalyst against both the typical chemical deactivation of homogeneous systems and leaching from heterogeneous systems. Cr-SIM-NU-1000 exhibits superior catalytic activity, as compared to Cr2O3, for ethylene oligomerization, with 20% conversion at a turnover frequency of about 60 h–1 and products ranging from C8–C28. Given that this catalysis occurs at low temperature (ambient) and low pressure (1 bar C2H4), along with minimal quantity of cocatalyst, the high activity shown by Cr-SIM-NU-1000 enables significant reduction in materials usage and waste. Postcatalytic characterization reveals Cr-SIM-NU-1000 remains intact with no leaching under the reaction conditions.

Polymers of intrinsic microporosity (PIMs) are promising materials for gas adsorption because of their high surface area, processability, and tailorable backbone. Specifically, nitrile groups on the backbone of PIM-1, an archetypal PIM, can be converted to other functional groups to selectively capture targeted gas molecules. Despite these appealing features of PIMs, their potential has mainly only been realized for the separation of nontoxic gases. Here, we prepared PIM-1 materials modified with carboxylic acid and amidoxime functional groups and investigated their performance as adsorbents for the capture of ammonia (NH3) and sulfur dioxide (SO2) gases. After determining the Brønsted acidity or basicity of the PIMs from potentiometric acid–base titrations, which can be correlated with affinity for acidic or basic toxic gases, we explored the uptake capacity toward NH3 and SO2, respectively. Gas sorption studies revealed that the carboxylated PIM showed higher affinity toward NH3 through the incorporation of Brønsted acid sites, while the amidoxime functionalized PIM exhibited affinity toward SO2 through the installed of slightly basic functional groups. Overall, this study highlights new insight into PIMs as solid sorbent materials for capturing toxic gases, which can be transferred to their potential use in practical applications, such as personal protective equipment or air filtration.

Organometallic iridium catalysts can be used in conjunction with bispinacolatodiboron (B 2 Pin 2 ) to effect the borylation of a variety of substrates such as arenes, alkanes, heteroarenes, and oxygenates. Recently, efforts have also focused on integrating these catalysts into porous supports, such as metal−organic frameworks (MOFs). While the mechanism of homogeneous borylation systems has been thoroughly investigated experimentally and computationally, analogous studies in MOF-supported iridium catalysts have not been conducted. Herein, we report the mechanistic investigation of a phenanthroline-iridium catalyst immobilized in the organic linker of Universitetet i Oslo (UiO)-67 (Zr 6 O 4 (OH) 4 (BPDC) 4 (PhenDC) 2 , BPDC = biphenyl-4,4′-dicarboxylate, PhenDC = 1,10-phenanthroline-4,4′-dicarboxylate). By using benzene as a model substrate, variable time normalization analysis (VTNA) of the kinetic data suggested a rate law consistent with zero-order in B 2 Pin 2 , and first-order in arene. A primary kinetic isotope effect (KIE) in the time course of benzene-d 6 borylation also provided complementary information about the role of the arene in the rate-determining step of the reaction. Characterization by techniques such as X-ray absorption spectroscopy (XAS) confirmed the presence of Ir(III), while pair distribution function (PDF) analysis suggested structures containing an Ir−Cl bond, further substantiated by X-ray photoelectron spectroscopy (XPS). Analysis of postcatalysis materials by inductively coupled plasma− optical emission spectroscopy (ICP-OES) revealed low boron accumulation, which may indicate an absence of boron in the resting state of the catalyst. Finally, in comparing borylation of benzene and toluene, a slight selectivity for benzene is observed, which is similar to the analogous homogeneous reaction, indicating the influence of substrate sterics on reactivity.

Ammonia (NH3) exposure has a serious impact on human health because of its toxic and corrosive nature. Therefore, efficient personal protective equipment (PPE) such as masks is necessary to eliminate and mitigate NH3 exposure risks. Because economically and environmentally viable conditions are of interest for large-scale manufacture of PPE, we herein report a benign procedure to synthesize a Zn-azolate metal–organic framework (MOF), MFU-4, for NH3 capture. The surface area and morphology of MFU-4 obtained in alcohol solvents at room temperature is consistent with that of traditionally synthesized MFU-4 in N,N-dimethylformamide at 140 °C. In addition to its large NH3 uptake capacity at 1 bar (17.7 mmol/g), MFU-4 shows outstanding performance in capturing NH3 at low concentration (10.8 mmol/g at 0.05 bar). Furthermore, the mild synthetic conditions implemented make it facile to immobilize MFU-4 onto cotton textile fiber. Enhanced NH3 capture ability of the MFU-4/fiber composite was also attributed to the well-exposed MOF particles. The benign synthetic MFU-4 procedure, high NH3 uptake, and easy integration onto fiber pave the way toward implementation of similar materials in PPE.