Linkage-polarized covalent organic frameworks couple antibiotic capture with triplet-sensitized singlet-oxygen oxidation.

Integrating antibiotic adsorption with photosensitized singlet oxygen (1O2) generation offers a promising approach to antibiotic removal from water. Linkage polarization was introduced into two topologically analogous covalent organic frameworks (COFs), coupling sulfadiazine (SDZ) capture with triplet-sensitized singlet oxygen generation. The repeating-unit dipole rose from 0.82 D in imine-linked TAT-Tca to 3.06 D in β-ketoenamine-linked TAT-Tp. In separate dark-adsorption experiments, TAT-Tp adsorbed approximately 30% of SDZ after 120 min, compared with 4% for TAT-Tca. Experimental and DFT computational evidence supported contributions from improved aqueous wettability and favorable hydrogen-bonding and aromatic interactions. Following 30 min of dark pretreatment, visible-light irradiation for 120 min resulted in total SDZ removal of approximately 95% for TAT-Tp, compared with 35% for TAT-Tca. Femtosecond transient absorption spectroscopy registered a fourfold extension of the excited-state absorption lifetime (143.12 versus 35.60 ps) and ground-state bleach recovery averaging 1588.70 ps for TAT-Tp. Delayed emission, quenching experiments, SOSG, and TEMP-EPR assigned the predominant oxidation route to triplet-mediated 1O2. TD-DFT calculations revealed stronger intraframework charge-transfer character and a smaller ΔEst for TAT-Tp. Together, the results show that β-ketoenamine formation combines enhanced SDZ retention with a more pronounced triplet-mediated 1O2 sensitization pathway, supporting a capture-coupled strategy for antibiotic treatment.