Pyridine Homopolymers Axial Ligation on Cobaloxime for Efficient Hydrogen Production

Photocatalytic hydrogen (H₂) production by mimicking natural light-harvesting complexes offers a sustainable route to solar fuel generation. Here, a pyridine-based homopolymer-chelated cobalt complex is reported as an efficient and stable catalyst for H₂ production via water splitting. This study introduces a series of reversible addition-fragmentation chain transfer (RAFT)synthesized homopolymers with pyridine moieties that axially coordinate to a cobaloxime core. This study investigates the effect of linker position (meta vs para) on proton reduction affinity in cobaloxime catalysts. The catalysts demonstrate potential for H₂ generation under visible light, with repetitive runs and maintain morphological integrity. Both photochemical and electrochemical H₂ production results align with and reinforce the catalytic efficacy of the system, achieving an H₂ generation rate of up to 42.99 mmol h^-1 g^-1 for P4VP-Co and 29.58 mmol h^-1 g^-1 for P3MP-Co in a neutral aqueous solution with a sacrificial electron donor. The superior electrochemical activity of P4VP-Co over P3MP-Co is due to the higher electroactive surface area in P4VP-Co. The density functional thoery (DFT) studies reveal the active site for the reaction and examine the role of homopolymers in enhancing H₂ evolution reaction. This study presents a unique example of a cobaloxime core chelated with electron-donating polymers for renewable energy conversion applications.