Photocatalytic Acetylene\nHydrochlorination by Pairing\nProton Reduction and Chlorine Oxidation over g‑C<sub>3</sub>N<sub>4</sub>/BiOCl Catalysts

Acetylene hydrochlorination is a vital industrial process\nfor the\nmanufacture of vinyl chloride monomer (VCM). Current thermocatalytic\nacetylene hydrochlorination requires toxic mercury-based or costly\nnoble metal-based catalysts, high temperatures (≥180 °C)\nand excessive gaseous HCl. Here, we report a room-temperature photocatalytic\nacetylene hydrochlorination strategy involving concurrent coupling\nof electron-driven proton reduction (*H) and hole-driven chloride\noxidation (*Cl) on photocatalyst surfaces. Under simulated solar light\nillumination, the developed noble-metal-free g-C<sub>3</sub>N<sub>4</sub>/BiOCl photocatalysts show a considerably high VCM production\nrate of 1198.6 μmol g<sup>–1</sup> h<sup>–1</sup> and a high VCM selectivity of 95% in a 0.1 M HCl aqueous solution.\nEven in chloride-rich natural seawater and acidified natural seawater,\nthe VCM production rates of g-C<sub>3</sub>N<sub>4</sub>/BiOCl photocatalysts\nare up to 170.3 μmol g<sup>–1</sup> h<sup>–1</sup> with a VCM selectivity of 80.4% and 1247.7 μmol g<sup>–1</sup> h<sup>–1</sup> with a VCM selectivity of 94.7%, respectively.\nMoreover, with sunlight irradiation and acidified natural seawater,\nthe g-C<sub>3</sub>N<sub>4</sub>/BiOCl photocatalysts in a large-scale\nphotosystem retain outstanding acetylene hydrochlorination performance\nover 10 days of operation. The radical scavenging, in situ photochemical\nFourier transform infrared spectroscopy, theoretical simulations,\nand control experiments reveal that active *Cl and *H play key roles\nin photocatalytic acetylene hydrochlorination via a possible reaction\npathway of C<sub>2</sub>H<sub>2</sub> → *C<sub>2</sub>H<sub>2</sub> → *C<sub>2</sub>H<sub>2</sub>Cl → *C<sub>2</sub>H<sub>3</sub>Cl → C<sub>2</sub>H<sub>3</sub>Cl. With respect\nto sustainability and low cost, this photocatalytic acetylene hydrochlorination\noffers excellent advantages over conventional thermocatalytic hydrochlorination\ntechnologies.