Molecular engineering of poly(amino)heptazine expands intra-molecular built-in electric field for efficient activation persulfate

Intramolecular D–A structures enable charge separation and transfer by precisely adjusting the electron affinity difference between donor and acceptor units at the molecular level. By adjusting the structure and ratio of donor and acceptor units, precise control of the band structure and photoelectric properties of D–A structures can be achieved, thereby enabling customized photocatalytic reactions. [Display omitted] •Intramolecular donor–acceptor conjugated CNS molecules have been synthesized.•CNS molecular framework results in establishing a robust intrinsic electric field.•Oxy-amino serves as an optimal activation site for activated persulfate. In the manipulation of π-conjugated organic polymer, strategic alterations to the polymerization cascade facilitate the integration of donor (D) and acceptor (A) entities within the polymer’s backbone. Such control is instrumental in broadening the photoresponse spectrum, enhancing photoinduced charge separation, and augmenting the efficiency of charge transfer processes. The oxygen-containing amino group (–ONH) was innovatively grafted into the polymerization process of the triazine-heptazine ring skeleton, and the –ONH was used as a capping agent to change the chain bonding in the polymerization process, thus a new intramolecular D–A structure was successfully constructed. Compared with the ordinary triazine-heptazine ring structure (CN), the new intramolecular D–A structure expanded the near-infrared absorption response range and had a strong intra-molecular built-in electric field (BIEF). Series of experiments in photocatalytic activation of persulfate showed that –ONH group could not only be used as an intramolecular acceptor, but also as an active site to activate persulfate as a free radical, which accelerated the ring-opening reaction of norfloxacin and realized effective mineralization in a short time. This work provides a potential reference for adjusting the molecular structure to solve the photo-response range and exciton dissociation efficiency in advanced oxidation.