image: Synthesis of the X–Por–COF (X = NN, CC, or C/C).
Credit: ©Science China Press
1. Three two-dimensional conjugated porphyrin-based COF materials (X–Por–COF, X = NN, CC, C/C) with tunable structural distortion were synthesized through precise molecular engineering of linker units. Specifically, the NN linker features a twisted structure connected by an N–N single bond, the CC linker consists of a partially twisted carbon–carbon double bond structure, while the C/C linker adopts a plana biphenyl configuration.
Comprehensive characterization via PXRD, N2/CO2 sorption isotherms, and electron microscopy revealed quantitative correlations between linker distortion degrees and material properties, including interlayer π-stacking modes and pore architecture regulation.
2. The experimental and theoretical calculation results indicate that the layered structure of NN–Por–COF exhibits wave like behavior due to the significant steric hindrance between the two carbazole units connected by N–N single bonds. This leads to a decrease in the stacking degree of interlayer porphyrin units, an increase in the number of exposed Co active sites, which is beneficial for mass transfer and CO2 reduction. In addition, the introduction of carbazole regulates the electronic structure of the Co active center, reducing the reaction energy barrier.
3. The NN–Por–COF photocatalyst exhibits exceptional photocatalytic CO2 reduction performance under precisely regulated catalytic conditions. In a pure CO2 atmosphere, it achieves a CO production rate of 22.38 mmol g−1 h−1. More remarkably, under simulated industrial flue gas conditions with dilute CO2 concentration (10%), it maintains superior activity of 3.02 mmol g−1 h−1, outperforming all reported state-of-the-art porphyrin-based photocatalysts to date.