Enhanced photocatalytic Cr(VI) reduction performance by novel PDI/COFs composite

Constructing the heterojunction by using covalent organic frameworks (COFs) is an effective way to promote photocatalytic activity. Herein, we designed and constructed different ratios of PDI/COFs hybrid materials by solvothermal method, denoted as PDI/TAPB-PDA (TAPB = 1,3,5-tris(4-aminophenyl)benzene, PDA = terephthaldehyde) composite. Although the construction of the heterojunction can destroy the long-range order of the TAPB-PDA COF structure to varying degrees, it does not affect the photocatalytic performance of PDI/TAPB-PDA composite. The optimal composite PDI/TAPB-PDA-5 with an initial molar ratio of PDI to TAPB-PDA COF of 32:1 has the highest photocatalytic performance for Cr(VI) reduction. The fitted first-order kinetic reaction rate k of PDI/TAPB-PDA-5 was 12.3 and 3.6 times that of PDI and TAPB-PDA COF, respectively. The superior photocatalytic activity of PDI/TAPB-PDA composite can be attributed to the broadened light absorption range and enhanced separation and transfer of carriers. The construction of composite materials between imine-linked COFs and dye PDI with excellent photocatalytic performance provides the possibility and affordability for realizing the practical application of expensive COFs-based catalysts.