Visible-light-driven photocatalytic CO2 reduction to formate over a zirconium-porphyrin metal–organic framework with shp-a topology

Abstract

In this study, a zirconium-porphyrin MOF (PCN-223) was synthesized, characterized and applied in the visible-light-driven photocatalytic CO₂ reduction. Drawing support from a highly conjugated 4-connected TCPP ligand and 12-connected zirconium based metal units, PCN-223 with shp-a topology exhibited an open-framework, good chemical stability, ligand-based broad light-absorption and fast photocurrent response (TCPP = tetrakis(4-carboxyphenyl)porphyrin). When used as a catalyst upon visible light irradiation, PCN-223 presented high efficiency for CO₂ reduction to formate with an average formate formation rate of 65.2 μmol h⁻¹ g_MOF⁻¹, which is higher than those of most reported Zr/Ti-MOFs under similar conditions. Photocatalytic experiments, Mott–Schottky measurements, electron paramagnetic resonance and photoluminescence tests demonstrated that dual catalytic routes exist in PCN-223 where the TCPP ligand and Zr–O clusters can both serve as catalytic centers for CO₂ reduction to formate. This study suggested that the combination of the porphyrin-based ligand and zirconium based metal clusters is an effective strategy for constructing MOF photocatalysts for CO₂ reduction.