Linkage orientation engineering of covalent organic frameworks enables flexible generation of reactive oxygen species in photocatalytic O2 activation

Photocatalytic O 2 activation, which produces miscellaneous reactive oxygen species (ROSs) via electron or energy transfer, is crucial for various chemical and biological processes. Unfortunately, controlling the exciton behaviors to flexibly regulate the generation of ROSs has rarely been explored and the underlying regulatory mechanisms remain poorly understood. Here, via linkage orientation engineering of covalent organic frameworks (COFs), we showcase a facile strategy for the flexible regulation between 1 O 2 and H 2 O 2 generation in photocatalytic O 2 activation. Imine-based COFs equipped with donor (D)-N=C-acceptor (A) chain (TFPT COFs) exerts effective H 2 O 2 production via electron transfer, while its structurally isomeric COFs with reversed imine orientation (TAPT COFs) tends to singlet oxygen ( 1 O 2 ) photosynthesis via energy transfer, attaining high efficiency for pollutant removal. Based on the results from ultrafast spectroscopy and theoretical calculations, when the N atom of the imine linkage is close to the electron acceptor, it diminishes the surface potential difference and increases the exciton binding energy; this favors the activation of the spin-triplet state excitons via an energy transfer process. Conversely, a strong built-in electric field is created when this N atom is adjacent to the electron donor, which encourages the dissociation of excitons into carriers and their subsequent separation.