Understanding the active-site nature of vanadia-based catalysts for oxidative dehydrogenation of ethylbenzene with CO2 via atomic layer deposited VOx on γ-Al2O3

•Highly dispersed VOx with controlled structures were synthesized via ALD.•Only isolated monomeric VOx was formed for A-1VAl.•The polymerization extent was increased with increasing the ALD cycles from 3 to 8.•The isolated VOx is more active and more stable than the polymeric VOx for CO2-ODEB.•The bridging VOAl bond is the key active site for CO2-ODEB.