One-pot Synthesis of Metal-coordinated Covalent Organic Frameworks for Enhanced CO2 Photoreduction

Solar energy-driven reduction of CO2 into fuels with H2O as a sacrificial agent is a challenging but desirable subject in photosynthesis. Covalent organic frameworks (COFs) are considered promising candidates for this subject because of their designable structures and functions. The coordination of transition metal ions into COFs is a feasible way to boost the photocatalytic activity. However, postsynthetic modification of COFs with metal ions often leads to a significant decrease in crystallinity and the specific surface area. Herein, we develop a one-pot synthesis of metal-coordinated (nonnoble metal) COFs with high crystallinity. HB-TAPT + Co with ordered and segregated D-A arrays is synthesized by combining 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT, a strong electron-acceptor) with 2-hydroxy-1,3,5-benzenetricarbaldehyde (HB)-loaded Co2+ (a strong electron-donor). The CO production when using HB-TAPT + Co under visible light irradiation for 4 h is 78.4 mu mol g-1, which is 3.2 times that of HB-TAPT + Co synthesized by the postsynthetic modification method and 2.65 times that of HB-TAPT without the metal ions. HB-TAPT + Co also has good recycling stability in photocatalytic CO2 reduction. Additionally, experimental results have demonstrated that the crystallinities of these metal-coordinated materials contribute greatly to the conversion of CO2 in the photoreaction with H2O. This work provides a new protocol for improving the CO2 photoreduction performance by coordinating metal ions to COFs while maintaining the original crystallinity through a one-pot synthesis method.