Heterogenization of Ru(bda) Molecular Catalyst with Redox-Active and Proton-Buffering Porphyrin Linkers for Acidic Water Oxidation

Abstract We report a porphyrin-bridged Ru(bda) coordination polymer integrated with carbon nanotubes, constructed from the well-defined homogeneous water oxidation catalyst in acid. The porphyrin linker simultaneously provides redox activity and proton-buffering functionality, enabling acidic water oxidation at an ultralow Ru loading (0.021 mgRu·cm–2). The resulting composite reaches current densities up to 200 mA·cm–2 in acid, exceeding previously reported molecular water oxidation catalyst-based anodes by one to two orders of magnitude. At identical metal loadings, it also outperforms both RuO2 and IrO2 benchmarks in both activity and stability. Electrochemical, spectroscopic, and theoretical results support porphyrin protonation and reversible oxidation, suggesting that ligand redox activity, together with proton management, contributes to the enhanced catalytic performance. These findings underscore the transformative potential of ligand engineering in molecular integration strategies for advancing artificial photosynthetic energy conversion systems.