Precise Integration of Photosensitizing and Catalytic Units into Stable Metal-Organic Frameworks for Efficient CO₂ Reduction

A series of multifunctional metal-organic framework (MOF) photocatalysts, Hf-IrF-DBP-M (M = Fe, Co, or Ni), were developed using a modular postsynthetic strategy that precisely integrates Ir-based photosensitizers (Ir-PSs) with transition metal catalytic units into a Hf-based MOF. This design enables systematic tuning of the interaction between metal sites and Ir-PSs to enhance photocatalytic CO₂ reduction. Among these, Hf-IrF-DBP-Fe exhibited the best performance, achieving CO turnover numbers of 3361 after 5 h and 8510 after 24 h of visible-light irradiation, with CO selectivity exceeding 98%. This activity is approximately 187 times higher than that of the Ir-PS-only control. Fluorescence quenching and electrochemical studies revealed efficient electron transfer from photoexcited and reduced Ir-PSs to the Fe center, facilitated by the ∼6 Å spatial proximity that promotes charge transport. Moreover, the Fe-based MOF also demonstrated excellent structural stability and recyclability, underscoring its potential as a robust platform for solar-driven CO₂ conversion.