Embedding a Dinuclear Ru─Pt Photocatalyst Into Polyampholytic Graft Copolymer Matrix Enables Prolonged Hydrogen Evolution While Allowing Catalyst Repair.

There are few molecular catalysts where active repair has been demonstrated, and one prominent example is a tetrapyridophenazine-bridged heterodinuclear Ru-Pt hydrogen-evolving photocatalyst, where hydrogenation of the pyrazine ring in the bridging ligand has been shown to lead to an end of photocatalytic activity. Subsequent in situ repair by persulfate enabled catalyst reactivation, but so far at the cost of decreasing catalytic activity over several repair cycles. We now show that tailored polyampholytic graft copolymers enable electrostatic immobilization of the photocatalyst in a unimolecular soft matter matrix, thereby prolonging (photo)catalytic activity due to slower photocatalyst degradation kinetics. We attribute this to a decreased propensity for hydrogenation of the pyrazine ring and, with that, slower degradation of the bridge and improved long-term HER activity, as evidenced by a holistic spectroscopic characterization of the molecular and electronic structure of the photocatalyst. At the same time, the graft copolymer matrix does not hinder oxidative repair of the photocatalyst, thus enabling multiple repair cycles without noticeable loss of catalytic activity. We therefore regard this as a novel blueprint for a synergistic molecule-in-matrix combination for sustainable light-driven catalysis.