Deformable Metal-Organic Framework Nanosheets for Heterogeneous Catalytic Reactions.

Abstract

The dynamic status near the surface of a catalyst can significantly affect the catalytic process, because the overall reaction rate depends on the mass velocity of product attachment and reactant detachment. As a dominant diffusion mechanism, molecular diffusion is known as a slow process that inhibits the fast contact between the reactants and the heterogeneous catalyst, which depresses catalytic conversion efficiency. Herein, we report a strategy that can break such a stagnant layer to facilitate the mass transport toward the catalyst surface, wherein Pd nanocubes (NCs) encapsulated in soft metal-organic framework (MOF) nanosheets are used as catalysts for the hydrogenation reactions. The soft MOF supports render deformable features to enhance mass transport across the Pd NCs, which is vital to enhance the catalyst performance. In combination with numerical simulations, we identify the deformable MOF driven by the shear force of flowing fluid to increase dye adsorption and catalytic conversion by 5- and 3-fold, respectively, as compared to a counterpart system containing nondeformable MOFs. The catalytic efficiency presents a volcano-type trend with the length-to-spacing ratio of MOF nanosheet being designed and reaches the maximum with a length-to-spacing ratio of 2:1. This technique provides unique opportunities to design a proof-of-concept self-propelled catalysis on the basis of a greater mechanistic understanding of heterogeneous catalytic reactions.