Cobalt and nickel coordinated guanidinium-based two-dimensional covalent organic framework nanosheets for efficient photocatalytic CO2 reduction

Photocatalytic CO 2 reduction to fuels and valuable chemicals by two-dimensional (2D) covalent organic framework nanosheets (CONs) is gathering much attention. However, it is still a challenge to improve photocatalytic performance. Herein, cobalt and nickel coordinated guanidinium-based 2D covalent organic framework nanosheets were synthesized by the condensation reaction between triformylphloroglucinol (TP) and triaminoguanidine (TG). In photocatalytic CO 2 reduction, CO 2 could be converted to CO effectively by using the prepared cobalt and nickel coordinated 2D CONs as photocatalyst. In particular, cobalt coordinated 2D guanidinium-based CONs (denoted as Co-TPTG Cl ) was the most effective, CO and H 2 production rate reached up to 14641 μ mol mg -1 h -1 and 7968 μ mol mg -1 h -1 , respectively. Compared with Ni-based catalyst, Co-based catalysts exhibited better catalytic performance in the photocatalytic CO 2 reduction. From the characterizations of fluorescence spectroscopy and CO 2 absorption-desorption isotherm, Co-TPTG Cl 2D CONs owns longer fluorescence lifetimes and better absorption capacity of CO 2 . • Cobalt and nickel coordinated guanidinium-based 2D CONs were prepared. • CO production rate reached up to 14641 μ mol mg -1 h -1 with Co-TPTG Cl as catalyst. • The recombination of photogenerated electrons and holes was inhibited effectively.