Post-synthetic modification of covalent organic frameworks with active manganese centers for electrocatalytic CO2 reduction in water

Abstract

The development of effective catalysts for the CO₂ reduction reaction (CO₂RR) is essential for transforming atmospheric CO₂ into valuable chemical scaffolds. While numerous catalysts have been developed for the CO₂RR, few are suitable for use in aqueous systems due to inherent design challenges. In this context, Covalent Organic Frameworks (COFs) have emerged as promising materials for the CO₂RR in water, offering potential solutions to these challenges. Thanks to their porosity, high surface area and crystalline structure, COFs are excellent hosts for single-atom catalysts (SACs), enabling the immobilization of high-value species and their utilization in heterogeneous catalytic processes. For this reason, we have explored the catalytic activity of a terpyridine–manganese complex integrated into a COF lattice, which was successfully synthesized and characterized, confirming the presence of the metal ion in the material with spectroscopic techniques such as XPS and EDS. This new material has proved to be an active heterogeneous catalyst for the CO₂RR in water as solvent, achieving a faradaic yield of 42% for CO at 300 mV overpotential and 16% for formate when 600 mV was applied. Furthermore, an ab initio theoretical study was performed to provide a plausible mechanism of the CO₂RR to elucidate the CO evolution pathway.