Effect of cobalt location in Keggin-type heteropoly catalysts on aerobic oxidation of cyclooctane: Experimental and theoretical study

•First study on the role of cobalt siting within the heteropoly structure in shaping the catalytic properties in liquid phase aerobic oxidation.•Mo-based catalysts proved more active than their tungsten twins, location of Co within the Keggin unit more beneficial than as a counter cation.•Experimental study is combined with DFT calculations which provide rationale for the observed patterns of catalytic behavior.•Higher reducibility of Mo-based anions, as compared to W-based ones, leads to the more favorable energetics of chain initiation and propagation.•The positive effect of Co addition is associated with opening of new pathways for oxygen activation and ROOH intermediate decomposition.