Electronic State and Microenvironment Modulation of Metal Nanoparticles Stabilized by MOFs for Boosting Electrocatalytic Nitrogen Reduction
Advanced Materials， Pub Date : 2023-03-04 , 

DOI: 10.1002/adma.202210669
Lulu Wen, Kang Sun, Xiaoshuo Liu, Weijie Yang, Luyan Li, Hai-Long Jiang

Modulation of the local electronic structure and microenvironment of catalytic metal sites plays a critical role in electrocatalysis, yet remains a grand challenge. Herein, PdCu nanoparticles with an electron rich state are encapsulated into a sulfonate functionalized metal-organic framework, UiO-66-SO3H (simply as UiO-S), and their microenvironment is further modulated by coating a hydrophobic polydimethylsiloxane (PDMS) layer, affording PdCu@UiO-S@PDMS. This resultant catalyst presents high activity toward the electrochemical nitrogen reduction reaction (NRR, Faraday efficiency: 13.16%, yield: 20.24 µg h−1 mgcat.−1), far superior to the corresponding counterparts. Experimental and theoretical results jointly demonstrate that the protonated and hydrophobic microenvironment supplies protons for the NRR yet suppresses the competitive hydrogen evolution reaction reaction, and electron-rich PdCu sites in PdCu@UiO-S@PDMS are favorable to formation of the N2H* intermediate and reduce the energy barrier of NRR, thereby accounting for its good performance.

https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202210669

Engineering Metal–Organic Frameworks for Selective Separation of Hexane Isomers Using 3-Dimensional Linkers
Journal of the American Chemical Society, Pub Date : 2023-03-10 ,

DOI: 10.1021/jacs.2c13715
Courtney S. Smoljan, Zhao Li, Haomiao Xie, Caitlin J. Setter, Karam B. Idrees, Florencia A. Son, Filip Formalik, Saman Shafaie, Timur Islamoglu, Lauren K. Macreadie, Randall Q. Snurr, Omar K. Farha

Metal–organic frameworks (MOFs) are highly tunable materials with potential for use as porous media in non-thermal adsorption or membrane-based separations. However, many separations target molecules with sub-angstrom differences in size, requiring precise control over the pore size. Herein, we demonstrate that this precise control can be achieved by installing a three-dimensional linker in an MOF with one-dimensional channels. Specifically, we synthesized single crystals and bulk powder of NU-2002, an isostructural framework to MIL-53 with bicyclo[1.1.1]pentane-1,3-dicarboxylic acid as the organic linker component. Using variable-temperature X-ray diffraction studies, we show that increasing linker dimensionality limits structural breathing relative to MIL-53. Furthermore, single-component adsorption isotherms demonstrate the efficacy of this material for separating hexane isomers based on the different sizes and shapes of these isomers.

https://pubs.acs.org/doi/abs/10.1021/jacs.2c13715

Construction of Monophosphine–Metal Complexes in Privileged Diphosphine-Based Covalent Organic Frameworks for Catalytic Asymmetric Hydrogenation
Journal of the American Chemical Society, Pub Date : 2023-03-10 ,

DOI: 10.1021/jacs.2c11037
Zehao Zheng, Chen Yuan, Meng Sun, Jinqiao Dong, Yan Liu, Yong Cui

Privileged diphosphine ligands that chelate many transition metals to form stable chelation complexes are essential in a variety of catalytic processes. However, the exact identity of the catalytically active moieties remains ambiguous because the chelated metal catalysts may undergo rearrangement during catalysis to produce monophosphine–metal complexes, which are hard to isolate and evaluate the activities. By taking advantage of the isolation of two phosphorus atoms, we demonstrate here the successful construction of chiral monophosphine–Ir/Ru complexes of diphosphine ligands in covalent organic frameworks (COFs) for enantioselective hydrogenation. By condensation of the tetraaldehyde of enantiopure MeO-BIPHEP and linear aromatic diamines, we prepare two homochiral two-dimensional COFs with ABC stacking, in which the two P atoms of each diphosphine are separated and fixed far apart. Post-synthetic metalations of the COFs thus afford the single-site Ir/Ru–monophosphine catalysts, in contrast to the homogeneous chelated analogues, that demonstrated excellent catalytic and recyclable performance in the asymmetric hydrogenation of quinolines and β-ketoesters, affording up to 99.9% enantiomeric excess. Owing to the fact that the porous catalyst is capable of adsorbing and concentrating hydrogen, the catalytic reactions are promoted under ambient/medium pressure, which are typically performed under high pressure for homogeneous catalysis. This work not only shows that monophosphine–metal complexes of diphosphines can be catalytically active centers for asymmetric hydrogenation reactions but also provides a new strategy to prepare new types of privileged phosphine-based heterogeneous catalysts.

https://pubs.acs.org/doi/10.1021/jacs.2c11037

Selective Methane Oxidation to Acetic Acid Using Molecular Oxygen over a Mono-Copper Hydroxyl Catalyst
Journal of the American Chemical Society, Pub Date : 2023-03-10 ,

DOI: 10.1021/jacs.2c12042
Neha Antil , Manav Chauhan , Naved Akhtar , Rahul Kalita , Kuntal Manna

Acetic acid is an industrially important chemical, produced mainly via carbonylation of methanol using precious metal-based homogeneous catalysts. As a low-cost feedstock, methane is commercially transformed to acetic acid via a multistep process involving energy-intensive methane steam reforming, methanol synthesis, and, subsequently, methanol carbonylation. Here, we report a direct single-step conversion of methane to acetic acid using molecular oxygen (O2) as the oxidant under mild conditions over a mono-copper hydroxyl site confined in a porous cerium metal–organic framework (MOF), Ce-UiO-Cu(OH). The Ce-UiO MOF-supported single-site copper hydroxyl catalyst gave exceptionally high acetic acid productivity of 335 mmolgcat–1 in 96% selectivity with a Cu TON up to 400 at 115 °C in water. Our spectroscopic and theoretical studies and controlled experiments reveal that the conversion of methane to acetic acid occurs via oxidative carbonylation, where methane is first activated at the copper hydroxyl site via σ-bond metathesis to afford Cu-methyl species, followed by carbonylation with in situ-generated carbon monoxide and subsequent hydrolysis by water. This work may guide the rational design of heterogeneous abundant metal catalysts for the activation and conversion of methane to acetic acid and other valuable chemicals under mild and environmentally friendly reaction conditions.

https://pubs.acs.org/doi/abs/10.1021/jacs.2c12042

Crystal Engineering Enables Cobalt-Based Metal–Organic Frameworks as High-Performance Electrocatalysts for H2O2 Production
Journal of the American Chemical Society , Pub Date : 2023-03-09 ,

DOI: 10.1021/jacs.2c11446
Chaoqi Zhang, Ling Yuan , Chao Liu, Zimeng Li, Yingying Zou, Xinchan Zhang, Yue Zhang, Zhiqiang Zhang, Guangfeng Wei , Chengzhong Yu

Metal–organic frameworks (MOFs) with highly adjustable structures are an emerging family of electrocatalysts in two-electron oxygen reduction reaction (2e-ORR) for H2O2 production. However, the development of MOF-based 2e-ORR catalysts with high H2O2 selectivity and production rate remains challenging. Herein, an elaborate design with fine control over MOFs at both atomic and nano-scale is demonstrated, enabling the well-known Zn/Co bimetallic zeolite imidazole frameworks (ZnCo-ZIFs) as excellent 2e-ORR electrocatalysts. Experimental results combined with density functional theory simulation have shown that the atomic level control can regulate the role of water molecules participating in the ORR process, and the morphology control over desired facet exposure adjusts the coordination unsaturation degree of active sites. The structural regulation at two length scales leads to synchronous control over both the kinetics and thermodynamics for ORR on bimetallic ZIF catalysts. The optimized ZnCo-ZIF with a Zn/Co molar ratio of 9/1 and predominant {001} facet exposure exhibits a high 2e– selectivity of ∼100% and a H2O2 yield of 4.35 mol gcat–1 h–1. The findings pave a new avenue toward the development of multivariate MOFs as advanced 2e-ORR electrocatalysts.

https://pubs.acs.org/doi/abs/10.1021/jacs.2c11446

General Strategy for Incorporation of Functional Group Handles into Covalent Organic Frameworks via the Ugi Reaction
Journal of the American Chemical Society, ub Date : 2023-03-09 ,

DOI: 10.1021/jacs.2c12440

Alexander Volkov, Jiashan Mi, Kanika Lalit, Puranjan Chatterjee, Dapeng Jing, Scott L. Carnahan, Yunhua Chen, Simin Sun, Aaron J. Rossini, Wenyu Huang*, and Levi M. Stanley*

The library of imine-linked covalent organic frameworks (COFs) has grown significantly over the last two decades, featuring a variety of morphologies, pore sizes, and applications. An array of synthetic methods has been developed to expand the scope of the COF functionalities; however, most of these methods were designed to introduce functional scaffolds tailored to a specific application. Having a general approach to diversify COFs via late-stage incorporation of functional group handles would greatly facilitate the transformation of these materials into platforms for a variety of useful applications. Herein, we report a general strategy to introduce functional group handles in COFs via the Ugi multicomponent reaction. To demonstrate the versatility of this approach, we have synthesized two COFs with hexagonal and kagome morphologies. We then introduced azide, alkyne, and vinyl functional groups, which could be readily utilized for a variety of post-synthetic modifications. This facile approach enables the functionalization of any COFs containing imine linkages.

https://pubs.acs.org/doi/abs/10.1021/jacs.2c12440

Covalent Organic Frameworks for Atmospheric Water Harvesting

Advanced Materials, Pub Date : 2023-03-09 , 

DOI: 10.1002/adma.202300018
Ha L Nguyen

• Ting He, Zhanfeng Zhao, Ruoyang Liu, Xinyan Liu, Bing Ni, Yanping Wei, Yinglong Wu, Wei Yuan, Hongjie Peng, Zhongyi Jiang*, and Yanli Zhao*