Modular optimization of metal-organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and photoreduce CO with high efficiency under visible-light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron-hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long-lived electrons for the reduction of CO molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO , which is equivalent to a 3.13-fold improvement in CO evolution rate (200.6 μmol g h ) and a 5.93-fold enhancement in CH generation rate (36.67 μmol g h ) compared to the parent MOF.

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The alkoxyl radical is an essential and prevalent reactive intermediate for chemical and biological studies. Here we report the first donor-acceptor complex-enabled alkoxyl radical generation under metal-free reaction conditions induced by visible light. Hantzsch ester forms the key donor-acceptor complex with N-alkoxyl derivatives, which is elucidated by a series of spectrometry and mechanistic experiments. Selective C(sp )-C(sp ) bond cleavage and allylation/alkenylation is demonstrated for the first time using this photocatalyst-free approach with linear primary, secondary, and tertiary alkoxyl radicals.