A defective nanodiamond-graphene material (ND@G) exhibits superior catalytic activity in acetylene hydrochlorination with an acetylene conversion of 50%, selectivity to vinyl chloride of up to 99.5% at 220 °C, and a C2H2 gas hourly space velocity of 300 h-1, which is the first example of a metal-free catalyst with comparable performance to that of the 0.25% Au/C catalyst.