Metal-organic frameworks (MOFs) are distinguished by their structural diversity, tunable electronic properties, and exceptional performance in various applications. Notably, the electron-donating ability of ligands significantly enhances the ligand-to-metal charge transfer (LMCT) processes within these frameworks, thereby promoting efficient charge migration. Herein, we developed two electron-rich macrocyclic ligands derived from phenothiazine- and phenoxazine-functionalized calix3arenes, alongside their corresponding cobalt-coordinated MOFs. Remarkably, the MOF designated as Co-C3PTZ-MOF─constructed using the more electron-donating calix3phenothiazine ligand (C3PTZ-COOH)─exhibited superior photoresponse and enhanced charge-transport characteristics. This optimized material achieved an exceptional CO2 photoreduction initial efficiency of 17,800 μmol g-1 h-1 with 81% CO selectivity. The outstanding photocatalytic performance originates from the strong electron-donating nature of the calix3arene-based ligands, which facilitated efficient LMCT processes. This study provides valuable insights for designing high-performance photocatalysts through rational engineering of macrocyclic ligands.
Zhang et al. (2025) studied this question.