Regulating Proton Supply for Selective Photocatalytic NO Conversion toward Pollutant Removal or Ammonia Recovery

Abstract Controlling the conversion of nitric oxide (NO) is critical for both air pollution mitigation and nitrogen resource recovery. Proton-coupled electron transfer (PCET) governs photocatalytic NO reduction, where reaction pathways determine whether nitrogen is removed as inert N2 or converted into value-added NH3. However, precise control over this selectivity remains challenging, largely due to the limited understanding and regulation of proton delivery. Alcohols with different α-C–H bond strengths are demonstrated to provide tunable proton fluxes. The energetics of α-C–H bonds in alcohol proton donors govern proton delivery and act as a molecular-level regulator for NO removal pathways. Ethanol, which contains a single and relatively inert α-C–H bond, cannot sustain proton delivery and therefore favors N–N coupling, leading to a N2 selectivity of 93.0%. In contrast, ethylene glycol contains two α-C–H positions that adjacent hydroxyl groups activate. As a result, the α-C–H cleavage barrier is lowered, continuous proton release is achieved, and NH3 formation is promoted with a selectivity of 98.3%. Proton generation and pathway selection are determined by α-C–H dehydrogenation, as evidenced by comprehensive mechanistic analyses using isotope-labeled in situ technologies. This work provides a molecular-level strategy for regulating PCET reactions through proton supply modulation, enabling scenario-adapted NO conversion for both pollutant removal and nitrogen resource recovery.