Tailored engineering of primary catalytic sites and secondary coordination spheres in metalloenzyme-mimetic MOF catalysts for boosting efficient CO2 conversion

Abstract

The fabrication of metalloenzyme-mimetic artificial catalyst is a promising approach to achieve maximum catalytic efficiency, but the rational integration of sophisticatedly optimized primary catalytic sites (PCS) and secondary coordination spheres (SCS) for specific transformation poses a grand challenge. Here in this work, we report the tailored engineering of Cu PCS and perfluoroalkyl SCS onto a zirconium-based framework [UiO-67-(BPY-Cu)-F_x (x = 3, 5, 7, 11)] [BPY = 2,2′-bipyridine-5,5′-dicarboxylate] that can be utilized in the highly efficient carboxylic cyclization reaction between propargylamines and flue gas CO₂. The perfluoroalkyl groups act as tunable SCS that can facilely adjust the surface electronegativity, hydrophobicity, as well as the CO₂ affinity and water vapor-resistance by simply varying the chain length. Meanwhile, the synergy between the Cu PCS and perfluoroalkyl SCS significantly facilitated the cyclization step by stabilizing the critical transition state, leading to the fast cyclization to the oxazolidinone ring. Owing to these features, UiO-67-(BPY-Cu)-F₇ exhibited remarkable metalloenzyme-mimetic catalytic behavior by greatly facilitating the binding of propargylamines and CO₂, promoting the stabilization of the critical transition state to cyclization, and boosting the releasing of oxazolidinones, which have been systematically investigated by the combination of substrate adsorption tests, in situ Fourier transform infrared spectra, grand canonical Monte Carlo simulations, density functional theory calculations, etc. Consequently, UiO-67-(BPY-Cu)-F₇ showed outstanding catalytic performance in the carboxylic cyclization of propargylamines and flue gas CO₂ under ambient conditions, exhibiting 64 times higher turnover frequency (TOF) than that of homogeneous or other MOF catalysts, and exhibiting the highest TOF under similar conditions. The present work not only provides an alternative strategy for the construction of advanced carboxylic cyclization systems, but also paves a new direction in the development of CO₂ conversion with exceptional activity through the tailored engineering of PCS and SCS in metalloenzyme-mimetic artificial catalysts.