Selective Photocatalytic Reduction of CO₂‐to‐CO in Water using a Polymeric Carbon Nitride Quantum Dot/Fe‐Porphyrin Hybrid Assembly

Abstract Visible light‐driven conversion of CO 2 into more value‐added products is a promising technology not only for diminution of CO 2 emission but also for solar energy storage in the form of chemical energy. However, photocatalytic materials that can efficiently and selectively reduce CO 2 ‐to‐CO in a fully aqueous solution typically involve precious metals that limit their suitability for large scale applications. Herein, a novel photocatalytic assembly is reported, consisting of polymeric carbon nitride quantum dots (CNQDs) as the visible light absorber and a Fe‐porphyrin complex (Fe‐ p ‐TMA) as the catalyst for CO 2 ‐to‐CO conversion. Both components were carefully selected to allow for excellent solubility in water as well as improved electronic communication through complementary electrostatic and π‐π interactions. This CNQD ⋅ [Fe‐ p ‐TMA] hybrid assembly, at the optimized molar ratio, can produce CO with a turnover number (TON) exceeding 10 5 and selectivity ∼96 % after 10 hours of visible light irradiation (400–700 nm). It is postulated that the enhanced CO 2 ‐to‐CO transformation performance is due to the convenience of a more direct charge transfer (CT) pathway between the CNQDs and [Fe‐ p ‐TMA] motif.