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.