Partial-Interpenetration-Controlled UiO-Type Metal-Organic Framework and its Catalytic Activity

Abstract

An unprecedented correlation between the catalytic activity of a Zr-based UiO-type metal-organic framework (MOF) and its degree of interpenetration (DOI) is reported. The DOI of an MOF is hard to control owing to the high-energy penalty required to construct a partially interpenetrated structure. Surprisingly, strong interactions between building blocks (inter-ligand hydrogen bonding) facilitate the formation of partially interpenetrated structures under carefully regulated synthesis conditions. Moreover, catalytic conversion rates for cyanosilylation and Knoevenagel condensation reactions are found to be proportional to the DOI of the MOF. Among MOFs with DOIs in the 0-100% range, that with a DOI of 87% is the most catalytically active. Framework interpenetration is known to lower catalytic performance by impeding reactant diffusion. A higher effective reactant concentration due to tight inclusion in the interpenetrated region is possibly responsible for this inverted result. Preparing partially interpenetrated metal-organic frameworks (MOFs) enables the relationship between MOF catalytic activity and degree of interpenetration to be understood. Substrate diffusion is no longer a catalytic kinetics determining factor when the interpenetrated MOF contains sufficiently large pores. High substrate affinity and the closely arranged catalytically active sites in the interpenetrated lattices cooperatively accelerate reactions.image