Dual Regulation of Reduction and Oxidation Center in Metal-Organic Frameworks to Boost CO₂ Photoreduction

The efficiency of photocatalytic CO₂ reduction is governed by multiple critical factors, including visible-light absorption, charge separation, hole utilization, and CO₂ adsorption/activation. However, simultaneous regulation of these factors in a single photocatalyst to facilitate CO₂ photoreduction remains underexplored. Herein, we proposed a dual-regulation strategy to concurrently modulate the reduction center via heteroatom substitution and the oxidation center via 2,2,6,6-tetramethylpiperidoxyl (TEMPO) coordination in cobalt porphyrin-based metal-organic frameworks (Co-MOFs), resulting in series of strong redox photocatalysts (TEMPO@Co-XN₃-MOF, X═N, O, and S) for efficient CO₂ photoreduction. Remarkably, CO yield with the dual-regulated TEMPO@Co-SN₃-PCN can reach 2000 µmol g^-1, over 10 and 50 times higher than that with single-regulated Co-SN₃-PCN and the typical Co-N₄-PCN, respectively. Moreover, the photogenegrated hole can efficiently drive the photooxidation of lactic acid to pyruvic acid with a 85% yield, while the in situ-generated CO is directly utilized in a tandem carbonylation reaction to afford benzophenone with a 90% yield. Investigations reveal that the dual regulation of redox centers endows TEMPO@Co-SN₃-PCN with efficient hole utilzation, efficient charge separation, strong CO₂ adsorption and activation, thereby facilitating green-synthesis of pyruvic acid and carbonyl compounds via a negative carbon emission process.