Steering single-site metallaphotocatalytic pathway by accumulated electron on carbon nitride support

Organic halide transformation is of high importance for fine chemical synthesis and environmental remediation. Integrated photocatalytic platforms open up distinctive reaction pathway for carbon-halogen bond activation/ reconstruction. Herein we reveal carbon nitride (CN)-ligated single atom nickel (Ni1/CN), with accumulated electron on the CN, paves Ni-mediated electron-proton transfer, enabling hydrodehalogenation, along with the catalytic carbon-oxygen (C-O) coupling. The preference for hydrodehalogenation positively correlates with density of electron on CN. EPR measurements suggest photo-generated NiI interacts with aryl halides, followed by electron transfer or reductive elimination to give different products. Further kinetic studies on hydrodehalogenation/C-O coupling show the reaction orders of 0.1/0.5 in aryl halide and 1.5/0.03 in (CN) electron, unveiling rate-determining step as oxidative addition to NiI and (CN) electron transfer for the two conversions. Our work advances in modulating aryl halide conversion by carrier accumulation on the photoactive support and guides metallaphotocatalytic platform design/operation toward target transformations.