Exciton Dissociation and Reactive Site Synergic Modulation in 3D Sulfur-Rich Conjugated Porous Polymers for Promoted Selectivity on CO2 Photoconversion

Conjugated porous polymers (CPPs) have garnered significant attention due to their desirable properties, such as structural stability, tunable band gap, and environmental friendliness. However, the influence of the precursor flexibility on the functionality of CPPs has not been thoroughly investigated. In this study, by selecting different building blocks (Ph = tetrakis­(4-ethynylphenyl)­methane and Py = 1,3,6,8-tetraethynylpyrene), sulfur-rich 3D CPPs of TTA-Py (TTA = tetrathienoanthracene) with rigid planar building blocks and TTA-Ph with flexible building blocks are synthesized via Sonogashira–Hagihara cross-coupling. Interestingly, compared with TTA-Py, TTA-Ph exhibits a larger specific surface area, improved CO2 adsorption capacity, and decreased energy barrier for the rate-determining step of CO2 photoconversion. The yield and selectivity of CO on flexible TTA-Ph are 322.05 μmol g–1 h–1 and 99.26%, respectively. Density functional theory (DFT) calculations show that the alkyne group is the reactive site of the materials. Furthermore, the interaction between this reactive site and the electron-donating functional group such as thienyl within the material promotes efficient exciton dissociation, which enhances the catalytic activity and selectivity of the materials. In particular, the effect of the conjugation degree on the performance is also explored by replacing the TTA core with the TTB core (TTB = tetrathienylbenzene). This work provides new insights to enhance the CO2 reduction activity of CPPs.