Red-Light-Driven CO2 Photoreduction into CH4 and CO Enabled by Narrow-Gap Conjugated Microporous Polymers

Herein, selective CO2 photoreduction into CH4 and CO with red light using conjugated microporous polymers (CMPs) at room temperature is reported. By incorporating electron-rich pyrene and electron-deficient fluorenone derivatives in the polymer networks to constructing intramolecular donor-acceptor system, the resulting three polymers show very broad light absorption covered from 350 to 1000 nm, with narrow gaps of 1.61-1.74 eV. In the presence of triethanolamine and 1-benzyl-1,4-dihydronicotinamide as the sacrificial agents, P3 exhibits the best visible-light reduction activity, with CH4 and CO evolution rates of 932.9 and 943.4 mu mol h(-1) g(-1), respectively. Most significantly, under the irradiation of red light (>600 nm), high evolution rates of CH4 and CO for P3 are achieved at 293.7 and 282.6 mu mol h(-1) g(-1), as well as nearly 100% reaction selectivity. The better performance of P3 than P1 and P2 can be ascribed to the high absorption toward CO2 and improved charge transfer under light irradiation. This work opens great opportunities for designing broadband-responsive CMPs for solar-driven photocatalytic conversion.