General Approach to Fe(II/III)-Terpyridine Coordination Polymer Gel Induced by X═O Compounds for Enhanced Photocatalytic CO2 Reduction in the Solid–Gas Phase

Herein, a chemical stimulation method to generate Fe-coordination polymer gels (Fe–CPG@stimulus) by adding X═O (X = C, N, S, P) compounds to Fe–B3Tpy complex solutions has been reported. During the gelation process, Fe³⁺ is reduced in situ to Fe²⁺, resulting in the formation of a metal–organic gel that incorporates both Fe²⁺ and Fe³⁺. Leveraging this versatile technique, a series of Fe–CPG@stimulus were achieved across diverse chemical stimuli. Additionally, the synthesized Fe–CPG@C₆O₆ demonstrates enhanced efficiency in CO₂ photoreduction to CO (44.82 μmol g^–1 h^–1) with approximately 100% selectivity, attributed to optimized structural stacking from in situ reduction and gel formation. Furthermore, a potential catalytic mechanism for the reduction of CO₂ to CO has been outlined by integrating data from in situ DRIFT spectroscopy and DFT calculations.