Morphology Control of Supramolecular Assembly for Superior CO2 Photoreduction

Coordination-driven metallo-supramolecular assemblies are potentially efficient catalysts in photocatalytic CO2 reduction. However, the relationship between morphology and photocatalytic performance remains barely explored. In this work, three metallo-supramolecular assemblies composed of Zn2+ and a flexible tris(terpyridine) ligand have been prepared for noble metal-free CO2 photoreduction on the basis of metal-ligand coordination, hydrogen bonding, and pi-pi stacking. The three assemblies possess distinct self-assembled morphologies including spherical particle, fibrous-like gel, and microrod. It has been found that the fibrous-like gel exhibits the best catalytic performance in photoreduction of CO2 to CO with a yield of 6.3 mmol g-1 h-1 and 94.7% selectivity over H2 generation. Photoelectrochemical measurements, photo-luminescence quenching experiments, and UV-vis absorption spectroscopy studies have demonstrated that the ligand-based electron transfer of the gel is more efficient compared with the other two assemblies.