A Hybrid Ru(II)/TiO Catalyst for Steadfast Photocatalytic CO to CO/Formate Conversion Following a Molecular Catalytic Route.

Herein, we employed a molecular Ru(II) catalyst immobilized onto TiO particulates of (4,4'-Y-bpy)Ru(CO)Cl (; Y = CHPO(OH)), as a hybrid catalyst system to secure the efficient and steady catalytic activity of a molecular bipyridyl Ru(II)-complex-based photocatalytic system for CO reduction. From a series of operando FTIR spectrochemical analyses, it was found that the TiO-fixed molecular Ru(II) complex leads to efficient stabilization of the key monomeric intermediate, Ru-hydride (LRu(H)(CO)Cl), and suppresses the formation of polymeric Ru(II) complex (-(L(CO)Ru-Ru(CO)L)-), which is a major deactivation product produced during photoreaction via the Ru-Ru dimeric route. Active promotion of the monomeric catalytic route in a hetero-binary system (IrPS + TiO/) that uses TiO-bound Ru(II) complex as reduction catalyst led to highly increased activity as well as durability of photocatalytic behavior with respect to the homogeneous catalysis of free Ru(II) catalyst (IrPS + Ru(II) catalyst). This catalytic strategy produced maximal turnover numbers (TONs) of >4816 and >2228, respectively, for CO and HCOO production in CO-saturated ,-dimethylformamide (DMF)/TEOA (16.7 vol % TEOA) solution containing a 0.1 M sacrificial electron donor.