Rational Design of Crystalline Covalent Organic Frameworks for Efficient CO₂ Photoreduction with H₂ O

Solar energy-driven conversion of CO₂ into fuels with H₂ O as a sacrificial agent is a challenging research field in photosynthesis. Herein, a series of crystalline porphyrin-tetrathiafulvalene covalent organic frameworks (COFs) are synthesized and used as photocatalysts for reducing CO₂ with H₂ O, in the absence of additional photosensitizer, sacrificial agents, and noble metal co-catalysts. The effective photogenerated electrons transfer from tetrathiafulvalene to porphyrin by covalent bonding, resulting in the separated electrons and holes, respectively, for CO₂ reduction and H₂ O oxidation. By adjusting the band structures of TTCOFs, TTCOF-Zn achieved the highest photocatalytic CO production of 12.33 μmol with circa 100 % selectivity, along with H₂ O oxidation to O₂ . Furthermore, DFT calculations combined with a crystal structure model confirmed the structure-function relationship. Our work provides a new sight for designing more efficient artificial crystalline photocatalysts.