A carbon supported carbon nitride is reported here as a catalyst for the direct conversion of acetylene and 1,2-dichloroethane (EDC) to vinyl chloride monomer (VCM). We demonstrate that increasing the synthesis temperature of the carbon nitride material leads to a catalyst with higher catalytic activity toward VCM production. The catalysts were characterized by acetylene temperature-programmed desorption, X-ray photoelectron spectroscopy, high-resolution TEM, electron energy loss spectroscopy, and computational methods, showing that the improved activity for the catalysts can be ascribed to both the higher proportion of pyridinic N and the more positive lowest unoccupied molecular orbital of the catalyst, resulting from the increased degree of polymerization of carbon nitride. These findings highlight the role of polymerization conditions in increasing the catalytic activity of carbon nitride catalysts and provide a strategy for the selective synthesis of highly active carbon nitride catalysts for the one-step synthesis of VCM from acetylene and EDC.