Enhancing CO₂ Photoreduction Efficiency Through Improved Interaction Enabled by a Decorated Covalent-Organic...

Photoreduction of CO₂ is often hindered by the sluggish kinetics for its activation. Refinement of host-guest interactions is an effective strategy to overcome this barrier. Here, we report the immobilization of active Co(II) sites within a covalent-organic framework (COF) with a one-dimensional (1D) chain structure, Co-PyPDA-COF, which demonstrates a remarkable CO generation rate of 30.5 mmol g^-1 h^-1 and a high CO selectivity of 95.8% in 2 h for CO₂ photoreduction at room temperature. The pore size of Co-PyPDA-COF is comparable to the diameter of CO₂, which allows simultaneous interaction of a single CO₂ molecule with the two Co(II) sites. The enhanced interaction result in increased local CO₂ pressure, limited CO₂ diffusion after adsorption, shortened distance for photoelectron transfer, and reduced energy barrier for the rate-determining step in CO₂ reduction, promoting CO₂ activation and conversion. This work opens a new way to design efficient catalysts by optimizing the pore size of the host.