Regulating the *OCCHO intermediate pathway towards highly selective photocatalytic CO 2 reduction to CH 3 CHO over locally crystallized carbon nitride

Locally crystallized PCN is prone to form *OCCHO groups rather than *CH 2 O groups, regulating the endoergic C–C coupling step to a simultaneous exoergic reaction and changing the reaction pathway towards CH 3 CHO (selectivity of 98.3%) instead of HCHO.