Metalloporphyrin-based covalent organic frameworks composed of the electron donor-acceptor dyads for visible-light-driven selective CO2reduction

The visible-light-driven photocatalytic CO(2)reduction with high efficiency is highly desirable but challenging. Herein, we present porphyrin-tetraphenylethene-based covalent organic frameworks (MP-TPE-COF, where M=H-2, Co and Ni; TPE=4,4 ',4 '',4"'-(ethane-1,1,2,2-tetrayl) tetrabenzaldehyde; COF=covalent organic framework) as ideal platforms for understanding photocatalytic CO(2)reduction at molecular level. Experimental and theoretical investigations have demonstrated crucial roles of metalloporphyrin units in selective adsorption, activation and conversion of CO(2)as well as in the separation of charge carriers and electron transfer, thus allowing for flexible modulation of photocatalytic activity and selectivity. CoP-TPE-COF exhibits high CO evolution rate of 2,414 mu mol g(-1)h(-1)with the selectivity of 61% over H(2)generation under visible-light irradiation, while NiP-TPE-COF provides CO evolution rate of 525 mu mol g(-1)h(-1)and 93% selectivity with superior durability. Moreover, the photocatalytic system is feasible for the simulated flue gas, which provides CO evolution rate of 386 mu mol g(-1)h(-1)and selectivity of 77%. This work provides in-depth insight into the structure-activity relationships toward the activation and photoreduction of CO2.