Visible-light photocatalytic selective oxidation of C(sp3)-H bonds by anion-cation dual-metal-site nanoscale localized carbon nitride

Selective oxidation of C(sp(3))-H bonds to carbonyl groups by abstracting H with a photoinduced highly active oxygen radical is an effective method used to give high value products. Here, we report a heterogeneous photocatalytic alkanes C-H bonds oxidation method under the irradiation of visible light (lambda = 425 nm) at ambient temperature using an anion-cation dual-metal-site modulated carbon nitride. The optimized cation (C) of Fe3+ or Ni2+, with an anion (A) of phosphotungstate (PW123-) constitutes the nanoscale dual-metal-site (DMS). With a Fe-PW12 dual-metal-site as a model (FePW), we demonstrate a A-C DMS nanoscale localized carbon nitride (A-C/g-C3N4) exhibiting a highly enhanced photocatalytic activity with a high product yield (86% conversion), selectivity (up to 99%), and a wide functional group tolerance (52 examples). The carbon nitride performs the roles of both the visible light response, and improves the selectivity for the oxidation of C(sp(3))-H bonds to carbonyl groups, along with the function of A-C DMS in promoting product yield. Mechanistic studies indicate that this reaction follows a radical pathway catalyzed by a photogenerated electron and hole on A-C/g-C3N4 that is mediated by the (BuO)-Bu-t and (BuOO)-Bu-t radicals. Notably, a 10 g scale reaction was successfully achieved for alkane photocatalytic oxidation to the corresponding product with a good yield (80% conversion), and high selectivity (95%) under natural sunlight at ambient temperature. In addition, this A-C/g-C3N4 photocatalyst is highly robust and can be reused at least six times and the activity is maintained.

Automated summary

The selective oxidation of C(sp(3))-H bonds to carbonyl groups using a photoinduced oxygen radical is an effective method to produce high value products. A photocatalytic oxidation of alkanes under visible light using an anion-cation dual-metal-site modulated carbon nitride has been successfully demonstrated, providing high product yield, selectivity, and functional group tolerance. The nanoscale dual-metal-site carbon nitride shows enhanced photocatalytic activity, serving as a highly robust catalyst for alkane oxidation under natural sunlight with good yield and selectivity.