Pore-Space Partition through an Embedding Metal-Carboxylate Chain-Induced Topology Upgrade Strategy for the Separation of Acetylene/Ethylene.

Ethylene (C2H4) is one of the most significant substances in the petrochemical industry; however, the capture of acetylene (C2H2) in about 1% from C2H2/C2H4 mixtures is a difficult task because of the similarity of their physical properties. With the aggravation of the energy crisis, using metal-organic framework (MOF) materials to purify C2H4 through adsorptive separation is a promising way to save energy and reduce emission. Pore-space partition (PSP) with the aim of enhancing the density of the binding sites and the strength of the host-guest interactions is an effective means to promote a solution for the challenging gas separation problems. Herein, we report a new embedding metal-carboxylate chain-induced topology upgrade strategy within a MOF to realize PSP and separation of C2H2/C2H4 mixtures. As a proof of concept, we construct a microporous MOF (NUM-12) utilizing the in situ insertion of cobalt terephthalic chains into a pretargeted ant-type framework during synthesis. Because of the attainment of an elaborately tuned aperture size and a specific pore environment through this strategy, NUM-12a (activated NUM-12) not only has a remarkable gas sorption capacity and strong interactions for C2H2 but also possesses an excellent purification performance for C2H2/C2H4 mixtures. Both experiments and simulation calculations clearly reveal that NUM-12 is a promising candidate for the separation of C2H2/C2H4, proving the feasibility of this new strategy for developing newly fashioned MOFs with adjustable structure and performance.

2-Methylimidazole-modulated 2D Cu metal-organic framework for 5-hydroxymethylfurfural hydrodeoxygenation.

Preparation of the high value-added chemical 2,5-dimethylfuran (2,5-DMF) from the biomass-derived platform molecule 5-hydroxymethylfurfural (HMF) is of great significance in the preparation of biofuels. Here, a bottom-up strategy was used to prepare a metal-organic framework (MOF) material with a two-dimensional nanosheet morphology, named CPM, in which an additive 2-methylimidazole was introduced into the hydrothermal process of Cu2+ ions and terephthalic acid. Subsequently, CPM-700 prepared by heat treatment under an inert atmosphere showed excellent catalytic performance in the reaction of HMF hydrodeoxygenation to 2,5-DMF. The materials before and after pyrogenation were characterized by PXRD, XPS, TEM, N2 adsorption and desorption and so on. It was confirmed that compared with the catalyst derived from the cubic MOF material self-assembled by Cu2+ and terephthalic acid, the morphology of 2D nanosheets was beneficial for the reaction of HMF to 2,5-DMF. Combined with the experimental data, the possible reaction path of 2,5-DMF preparation from HMF is that 2,5-dihydroxymethylfuran was formed by hydrogenation of the aldehyde group on the furan ring, and then 2,5-DMF was obtained by hydrogenolysis. This paper provides an effective route for 2D MOF-derived catalytic materials in the selective hydrogenation of HMF.

In Situ Construction of a Co/ZnO@C Heterojunction Catalyst for Efficient Hydrogenation of Biomass Derivative under Mild Conditions.

The efficient hydrogenation of biomass-derived levulinic acid (LA) to value-added γ-valerolactone (GVL) based on nonprecious metal catalysts under mild conditions is crucial challenge because of the intrinsic inactivity and instability of these catalysts. Herein, a series of highly active and stable carbon-encapsulated Co/ZnO@C-X (where X = 0.1, 0.3, 0.5, the molar ratios of Zn/(Co+Zn)) heterojunction catalysts were obtained by in situ pyrolysis of bimetal CoZn MOF-74. The optimal Co/ZnO@C-0.3 catalyst could achieve 100% conversion of LA and 98.35% selectivity to GVL under mild conditions (100 °C, 5 bar, 3 h), which outperformed most of the state-of-the-art catalysts reported so far. Detailed characterizations, experimental investigations, and theoretical calculations revealed that the interfacial interaction between Co and ZnO nanoparticles (NPs) could promote the dispersibility and air stability of the active Co0 for the activation of H2. Moreover, the strong Co-ZnO interaction also enhanced the Lewis acidity of the Co/ZnO interface, contributing to the adsorption of LA and the esterification of intermediates. The synergy between the hydrogenation sites and the Lewis acid sites at the Co/ZnO interface enabled the conversion of LA to GVL with high efficiency. In addition, benefiting from the Co-ZnO interfacial interaction as well as the unique carbon-encapsulated structure of the heterojunction catalyst, the recyclability was also greatly improved and the yield of GVL was nearly unchanged even after six cycles.

Encapsulation of Ultrafine Metal-Organic Framework Nanoparticles within Multichamber Carbon Spheres by a Two-Step Double-Solvent Strategy for High-Performance Catalysts.

Carbon-encapsulated metal-organic framework (MOF) composite is one kind of emerging new catalyst with high efficiency and has gained much attention. However, for this kind of composite catalyst, the key to improving its catalytic activity and durability is to realize the effective dispersion of MOF nanoparticles (NPs) and enhance the interaction between MOF NPs and the carbon matrix, which remain a significant challenge. Herein, ultrafine MOF NPs within multichamber carbon spheres (MOF@MCCS), for the first time, have been rationally synthesized by a two-step double-solvent strategy for high-performance catalysts. The precise loading of guest MOFs can be achieved by adjusting the multichamber structure and calcination extent of the multichamber polymer (MCP), and the particle size of MOFs can be as low as 13.2 nm. Due to the formation of abundant carbon defects in the pyrolysis process of MCPs, the special structure and synergistic effect make the material exhibit higher catalytic activity and durability. More importantly, this method is universal and can be extended to different MOF systems. The two-step double-solvent strategy not only prepares a unique structure of MOF@MCCS-type host-guest-encapsulated catalysts but also provides a new idea for the design of high-efficiency catalysts with better performance and higher durability.