Kinetic Control via Binding Sites within the Confined Space of Metal Metalloporphyrin-Frameworks for Enhanced Shape-Selectivity Catalysis

One striking feature of enzyme is its controllable ability to trap substrates via synergistic or cooperative binding in the enzymatic pocket, which renders the shape-selectivity of product by the confined spatial environment. The success of shape-selective catalysis relies on the ability of enzyme to tune the thermodynamics and kinetics for chemical reactions. In emulation of enzyme's ability, we showcase herein a targeting strategy with the substrate being anchored on the internal pore wall of metal-organic frameworks (MOFs), taking full advantage of the sterically kinetic control to achieve shape-selectivity for the reactions. For this purpose, a series of binding site-accessible metal metalloporphyrin-frameworks (MMPFs) have been investigated to shed light on the nature of enzyme-mimic catalysis. They exhibit a different density of binding sites that are well arranged into the nanospace with corresponding distances of opposite binding sites. Such a structural specificity results in a facile switch in selectivity from an exclusive formation of the thermodynamically stable product to the kinetic product. Thus, the proposed targeting strategy, based on the combination of porous materials and binding events, paves a new way to develop highly efficient heterogeneous catalysts for shifting selectivity.

Automated summary

One striking feature of enzymes is their ability to trap substrates and produce shape-selective products through synergistic or cooperative binding in their enzymatic pocket. In this study, we demonstrate a targeting strategy by anchoring substrates on the internal pore wall of metal-organic frameworks (MOFs), mimicking the enzyme's ability and achieving shape-selectivity for reactions. By investigating metal metalloporphyrin-frameworks (MMPFs) with different densities and distances of binding sites, we show that the structural specificity of MMPFs allows for a facile switch in selectivity, from thermodynamically stable product to kinetic product. Thus, this proposed targeting strategy using porous materials and binding events provides a new approach for developing highly efficient heterogeneous catalysts for shifting selectivity.