Modulating Active Center Microenvironment in Phthalocyanine-Based Covalent Organic Frameworks for Enhanced Electrocatalytic CO2 to CH3OH.

Developing catalysts for electrocatalytic CO2 to CH3OH still faces great challenge due to the involvement of multiple proton-coupled electron transfer (PCET) processes. Molecular phthalocyanine electrocatalysts on carbon nanotubes have achieved production of methanol as the sole liquid-phase product but with the activity and stability far from meeting industrial demands. Herein, phthalocyaninato cobalt is fabricated into covalent organic frameworks PE-COF via polymerization with ellagic acid. Subsequent hydrolyzation of the ester groups in this framework affords COOH/OH-containing PEH-COF, resulting in the successful modulation over the local microenvironment of Co as electrochemical active center and in turn rendering the production of CH3OH with high yield and durability. Experimental and theoretical investigations reveal that construction of the COOH group and H2O participated catalytic cages in PEH-COF can effectively fix hydrated potassium ions, which efficiently enhances the PCET kinetics and lowers the energy barriers for the conversion of CO2 to CH3OH. The partial current density (j) and Faraday efficiency of methanol for PEH-COF could reach 100.9 mA cm-2 and 38.5%, respectively. Moreover, the j C H 3 O H $\mathrm{j}_{{CH}_3OH}$ of PEH-COF can be maintained at 100.4 mA cm-2 after 9 h of electrocatalysis, superior to the thus far reported catalysts.