Microwave-assisted deposition of a highly active cobalt catalyst on mesoporous silica for photochemical CO2 reduction.

Coupling with robust surfaces is a promising approach to improve the stability and recyclability of highly active molecular catalysts. This study builds on our prior success to deposit a Co(iii) cyclam complex, where cyclam is 1,4,8,11-tetraazacyclotetradecane, on mesoporous silica via a microwave-assisted process. The Co(iii) complex was successfully deposited on the silica surface through reacting with silanol groups in the silica mesopores. The resulting surface Co(iii) catalyst was characterized by different techniques and tested in photochemical CO2 reduction in the presence of p-terphenyl as a photosensitizer. The synthesized Co(iii) catalyst showed significantly higher activity and selectivity than the unbound Co(iii) cyclam complex and a surface Co(iii) catalyst prepared by other methods. Microwave-assisted heating was found to be essential for the deposition of uniform Co(iii) sites in the silica mesopores, which likely accounts for the superior activity and selectivity of the synthesized surface Co(iii) catalyst.