A series of porous poly(ionic liquid)s (PILs) were synthesized using an innovative method which involves the synthesis of non-ionic co-polymers such as divinylbenzene and vinylimidazole, followed by an alkylation step to introduce the ionic liquid functionality in the polymeric matrix. This synthetic strategy allowed us to obtain tunable imidazolium type PILs having simultaneously high surface area and exposed ionic moieties. A set of PILs was obtained by changing systematically the alkyl chains, the anions and the cross-linking degree. This approach allowed us to elucidate the effect of each synthetic variable on the catalytic performances of PILs towards the carbon dioxide cycloaddition reaction under very mild conditions (room temperature and low pressure). Finally, in situ FTIR spectroscopy allowed us to establish a relationship between the structure of PILs and their catalytic properties.