Charge-Transfer Regulated Visible Light Driven Photocatalytic H2 Production and CO2 Reduction in Tetrathiafulvalene Based Coordination Polymer Gel

Abstract The much-needed renewable alternatives to fossil fuel can be achieved efficiently and sustainably by converting solar energy to solar fuels via hydrogen generation from water or CO2 reduction. In this regard, a soft processable metal-organic hybrid semiconducting material has been developed and studied for photocatalytic activity towards H2 production and CO2 reduction to CO and CH4 under visible light and direct sunlight irradiation. A tetrapodal low molecular weight gelator is synthesized by integrating tetrathiafulvalene and terpyridine through amide linkage (TPY-TTF). The TPY-TTF acts as a linker and by self-assembly with ZnII results in a charge-transfer (CT) coordination polymer gel (CPG); Zn-TPY-TTF. The Zn-TPY-TTF shows impressive photocatalytic activity towards H2 production (rate = 530 μmol g-1h-1) and CO2 reduction to CO (rate = 438 μmol g-1h-1, selectivity >99%) regulated by charge-transfer interaction. Furthermore, in-situ stabilization of Pt nanoparticles to CPG (Pt@Zn-TPY-TTF) exhibits remarkably enhanced H2 evolution (rate =14727 μmol g-1h-1). Importantly, Pt@Zn-TPY-TTF modulate the CO2 reduction from CO to CH4 (rate = 292 μmol g-1h-1, selectivity >97%). Real-time CO2 reduction reaction is monitored by in-situ DRIFT study and subsequent plausible mechanism is derived computationally. The photocatalytic activity of Zn-TPY-TTF and Pt@Zn-TPY-TTF composite was also examined under sunlight that display excellent H2 evolution and CO2 reduction.