Single-Atom Copper Catalyst Enables Reusable, Light-Driven N-Demethylation

A recyclable, noble-metal-free photocatalyst composed of atomically dispersed Cu on functionalized graphitic carbon nitride (Cu@f-gC3N4) enables selective N-demethylation and N-dealkylation of a broad range of tertiary amines under 390 nm light in an O2 atmosphere. The reaction tolerates diverse substrates, including pharmaceutically relevant molecules, and can be scaled to 10 mmol with catalyst reuse exceeding ten cycles. Mechanistic studies (radical trapping, isotope labeling, in situ FTIR, EPR, XANES/EXAFS and DFT) support a photoredox pathway in which amine oxidation generates ammonium-like intermediates, O2 is reduced to superoxide to abstract a methyl hydrogen, forming an iminium that hydrolyzes to the secondary amine; the Cu single-atom sites and the functionalized g-C3N4 support drive charge separation and O2 activation, enabling practical late-stage amine diversification without sacrificial reagents.