• • Achieved H2O2 production rate of 4777 μmol g−1 h−1 under visible light, representing a 3.2-fold improvement over unoptimized counterparts; this rate is among the highest reported for metal-free COF photocatalysts, indicating potential for industrial-scale solar-driven H2O2 synthesis.
• • O2 utilization and conversion efficiency reached 99.3%, ensuring near-stoichiometric use of generated oxygen; this minimizes feedstock waste and enhances process economics for decentralized H2O2 production.
• • The optimized AA-COF operates in pure water and air without sacrificial agents, eliminating costs and contamination associated with organic hole scavengers; this simplifies downstream purification and reduces operational hazards.
• • Single-carbon atomic engineering (varying aliphatic chain length) fine-tuned the hydrophilicity and O2 affinity, achieving a kinetic balance between ORR and WOR; this design principle can be extended to other COF systems to address similar kinetic mismatches.