Engineering frustrated Lewis pairs on graphitic carbon nitride for efficient photocatalytic degradation and detoxification of tetracycline

Heterogeneous photocatalysis is a promising advanced oxidation process for the removal of organic pollutants, yet its efficiency is often limited by thermodynamic barriers and insufficient pollutant activation. Herein, we report the construction of frustrated Lewis pairs (FLPs) on graphitic carbon nitride (CN) to address these challenges and achieve enhanced photocatalytic degradation of tetracycline (TC). FLPs are introduced by an alkalization treatment, which introduces carbon vacancies (CVs) as Lewis acid (LA) sites and adjacent surface hydroxyl groups as Lewis base (LB) sites. This unique dual-sites configuration markedly improves charge separation, optimizes the band structure, and enhances the redox potential of CN. Furthermore, the synergistic “push–pull” electron effect of FLPs enables efficient activation of TC molecules, facilitating rapid oxidation by photogenerated holes. As a result, the optimized catalyst (CN-OH-15) achieves a degradation rate constant of 0.045 min⁻¹, nearly four times higher than pristine CN. Mechanistic studies reveal that the degradation pathway proceeds through demethylation, decarbonylation and ring-opening reactions, effectively reducing the toxicity of intermediates and creating a favorable basis for integration with biological treatment. This study demonstrates FLP engineering as a powerful strategy for pollutant activation and to regulate degradation pathways for sustainable wastewater remediation.