Rational Design of Polymers for Selective CO Reduction Catalysis.

A series of copolymers comprising a terpyridine ligand and various functional groups were synthesized toward integrating a Co-based molecular CO reduction catalyst. Using porous metal oxide electrodes designed to host macromolecules, the Co-coordinated polymers were readily immobilized via phosphonate anchoring groups. Within the polymeric matrix, the outer coordination sphere of the Co terpyridine catalyst was engineered using hydrophobic functional moieties to improve CO reduction selectivity in the presence of water. Electrochemical and photoelectrochemical CO reduction were demonstrated with the polymer-immobilized hybrid cathodes, with a CO:H product ratio of up to 6:1 compared to 2:1 for a corresponding "monomeric" Co terpyridine catalyst. This versatile platform of polymer design demonstrates promise in controlling the outer-sphere environment of synthetic molecular catalysts, analogous to CO reductases.