A Fully Conjugated Benzo[1,2-b:4,5-b′]Dithiophene-Based Covalent Organic Framework Enables Efficient Blue Light-Driven Photocatalytic Sulfoxidation

Covalent organic frameworks (COFs) are becoming increasingly attractive in photocatalytic transformations because of the designable structures grounded on the building blocks and linkages. Herein, benzo[1,2-b:4,5-b′]dithiophene, essential for various organic optoelectronic materials, is adopted as the building block for COFs. Hence, a fully conjugated COF BDTT-sp²c-COF and an imine-linked COF BDTT-COF are constructed by the condensations of 5′,5″″-(benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis([1,1′:3′,1″-terphenyl]-4,4″-dicarbaldehyde) with p-phenyldiacetonitrile and p-phenylenediamine, respectively. Thorough characterizations and theoretical calculations disclose that BDTT-sp²c-COF is superior to BDTT-COF in terms of specific surface area, photocarrier separation, and electron transfer. As such, BDTT-sp²c-COF enables more efficient photocatalytic sulfoxidation with oxygen than BDTT-COF. The fully conjugated structure guarantees the recyclability of BDTT-sp²c-COF. The blue light-driven photocatalytic sulfoxidation is generally applicable and proceeds selectively via energy and electron transfers with oxygen over BDTT-sp²c-COF. The fully conjugated COFs are promising to enable efficient photocatalytic reactions.