Promoting exciton dissociation of covalent organic frameworks via donor-acceptor characteristic modulation for enhanced HO photocatalytic production.

Post-synthetic modification (PSM) offers a promising approach for tailoring the compositional, structural, and electronic properties of covalent organic frameworks (COFs), thereby enhancing their exciton dissociation ability and facilitating charge transfer. The effectiveness of these approaches is largely compromised by the harsh conditions, complexity, and alteration of the original structure. Therefore, developing a facile yet effective PSM for modulating COFs' properties without altering the original geometry and/or structure is a challenge. By introducing a phosphazene moiety, ca. hexachlorocyclotriphosphazene (CP), as a donor scaffold, we fabricated a CP-modified triazine-based COF (TDCP COF) with a donor-acceptor (D-A) configuration, via a facile one-step PSM method, and used it for photocatalytic conversion of O into HO. The resultant TDCP COF with D-A characteristic and substantial intramolecular dipole moment displays a facilitated exciton dissociation and charge transfer. The modified TDCP COF not only provides more favorable adsorption sites for O molecules, but also manipulates the O activation pathways through multiple mechanisms into •O and singlet oxygen (O). Benefiting from these features, the TDCP COF exhibited a three times higher HO production rate compared to TD. This work sheds light on a facile yet effective PSM strategy for the development of highly efficient COFs applied for various applications, including photocatalysis, organic solar cells, drug delivery, and gas separation.