Fused Porphyrin Thin Films as Heterogeneous Visible-Light Active Photocatalysts with Well-Defined Active Metal Sites for Hydrogen Generation

Metalloporphyrin-based photocatalysts have attracted great interest due to their high extinction coefficient in the visible range coupled to a catalytically active central metal ion surrounded by a highly conjugated heterocyclic macrocycle. In this work, fused copper(II) porphyrin-based conjugated polymer thin films are shown to be active electrocatalysts and photocatalysts for the heterogeneous hydrogen evolution reaction (HER). The fused copper(II) porphyrin thin films notably show a significant reduction of the overpotential required for HER in comparison to the reference nonfused porphyrin thin films. More importantly, in-depth high-resolution mass spectrometry reveals how the porphyrin substituents influence the catalytic performance of the films, with phenyl substituents enabling superior photocatalytic performances over mesityl substituents, providing insights for the engineering of heterogeneous catalysts based on fused metalloporphyrins.