Lattice Strain in Multi-Component Covalent Organic Frameworks for Enhanced H₂O₂ Photosynthesis

The structural designability of donor-acceptor (D-A) covalent organic frameworks (COFs) makes these systems the promising candidates for photocatalytic H₂O₂ synthesis, however, most D-A COFs are constructed by one electron-rich building block with one electron-deficient building unit, which are short of accuracy in modulating the electron structure, herein, condensation reactions between electron-deficient 4,4,4″-(1,3,5-benzenetriyltri-2,1-ethynediyl)tris-benzenamine (TAEB) and the mixture of electron-rich benzo[1,2-b:3,4-b':5,6-b″]trithiophene-2,5,8-tricarboxaldehyde (BTT) and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TPT) were carried out with the ratio of BTT and TPT changing from 8:2, 6:4, 4:6, to 2:8, generating a series of three-component COFs, named as BTTP-x:(10-x) (x = 8, 6, 4, and 2). The lattice strain of the frameworks is revealed to be adjusted with the change in the ratio of BTT and TPT, achieving accurate modulation for the local electron structure of active sites, proving the advantage of three-component COFs system. Particularly, this in turn leads to the optimized catalytic performance of BTTP-2:8 toward H₂O₂ photosynthesis from H₂O and O₂ with a production rate of 15498 µmol g^-1 h^-1, an apparent quantum yield of 28.45% at 420 nm, and a solar-to-chemical conversion efficiency of 2.74%, superior to most photocatalysts reported thus far. The present result should be helpful for developing highly efficient photocatalysts toward H₂O₂ synthesis.