Non-Covalent Host-Guest Extraction of Methanol Enables Enhanced Syngas-to-Methanol Conversion Over Hybrid Oxide-Porous Framework Catalysis.

Abstract

Product formation is commonly regarded as the endpoint of heterogeneous catalysis, yet the subsequent fate of products near active surfaces critically affects catalytic turnover. For syngas-to-methanol conversion over Cu/Zn/Al (CZA) catalysts, product retention and re-adsorption represent an underappreciated limitation governing both activity and selectivity. Methanol generated at metal-oxide interfaces tends to remain near active sites, where interactions with surface hydroxyls trigger secondary reactions such as the water-gas shift. By physically mixing commercial CZA with hydrogen-bond-rich porous frameworks, we introduce a non-covalent host-guest extraction pathway that captures methanol from the interfacial region and facilitates its release into the gas phase. This extraction shifts the local adsorption-desorption equilibrium, suppresses methanol re-adsorption, and boosts methanol space-time yield by 1.12-1.43 times relative to pristine CZA, while retaining > 92.3% selectivity. In situ spectroscopy, transient kinetics, and simulations confirm the porous framework acts as a molecular sink, regulating methanol residence time and transport without direct catalytic participation. This effect is general across distinct metal-organic and covalent organic frameworks, establishing non-covalent extraction as a transferable strategy. This work demonstrates that non-covalent control of product desorption and transport serves as a complementary design principle for heterogeneous catalysis beyond conventional active-site engineering.