Fibrous Pb(II)‐Based Coordination Polymer Operable as a Photocatalyst and Electrocatalyst for High‐Rate, Selective CO₂‐to‐Formate Conversion

Abstract

A nonporous [Pb(tadt)]n (tadt = 1,3,4‐thiadiazole‐2,5‐dithiolate) coordination polymer, KGF‐9, with a 2D infinite (−Pb−S−)n structure has been previously reported as a precious‐metal‐free photocatalyst for selective CO2‐to‐formate conversion under visible light. In the present work, a microwave (MW)‐assisted solvothermal reaction is used to synthesize KGF‐9 with improved physicochemical properties and catalytic activity. Compared with KGF‐9 prepared by the previously reported methods, that prepared by the new synthesis route exhibited a greater specific surface area, greater crystallinity, and greater photoconductivity. These improved properties led to a drastic increase of the apparent quantum yield (AQY) for selective formate production, from 2.6 to 25% at 400 nm; this AQY represents a record‐high value among reported heterogeneous photocatalysts for CO2‐to‐formate conversion. Interestingly, the AQY for formate production is unchanged irrespective of the light intensity (0.04–14 mW cm−2), indicating little contribution of charge accumulation in the bulk during the reaction (i.e., indicating efficient charge transport to surface reactants). When composited with Ketjen Black, KGF‐9 enabled the electrochemical conversion of CO2 to formate in aqueous solution while maintaining a high selectivity. A high‐rate reduction of CO2 to formate with a total absolute current density of 200–300 mA cm−2 is achieved, with a Faradaic efficiency (FE) of >90%.