Manipulating d-Band Center and d–p Orbital Coupling to Mitigate Adsorption–Desorption Trade-Off for Efficient CO2-to-CO Photoreduction over MOF Nanofibers

The strong CO 2 adsorption and facile CO desorption are a trade-off issue for CO 2 -to-CO photoreduction pathways. Synchronous optimization of these two steps remains a substantial hurdle and has been less explored. Herein, an O/N mixed coordinated Co-NTA (NTA: nitrilotriacetic acid), featuring an ultralong nanofiber architecture, is reported for efficient CO 2 photoreduction. The mixed coordination can regulate the positions of d -band center of Co sites and also d – p orbital coupling with coordination atoms, which are recognized as main activity descriptors. Consequently, free energies of both steps of CO 2 →*CO 2 and *CO→CO are well optimized, making the CO 2 -to-CO photoreduction pathways more favorable thermodynamically. By contrast, the classic N-coordinated Co-MeIm (MeIm: 2-methylimidazole) and O-coordinated Co-BDC (BDC: 1,4-benzenedicarboxylic acid) suffer from unfavorable CO 2 adsorption and intractable CO desorption, respectively. In addition, achiral NTA molecules can direct the growth of Co-NTA into one-dimensional (1D) nanofibers, while Co-BDC and Co-MeIm possess typical 2D nanosheet and 3D polyhedron architectures. The fast electron transport along the axis directions makes charge-transfer kinetics most efficient over 1D Co-NTA. The thermodynamic and kinetic benefits jointly contribute to the 1.8-fold increase in CO production over 1D Co-NTA.