Coupling polymer and ionic liquids with electrodes for catalysis is a promising tool for optimization of electrocatalytic CO2 reduction reaction (CO2RR). Here, block copolymer ionic liquids BCPILs were synthesized via controlled radical polymerization and nucleophilic post-substitution to introduce imidazole moieties. We show that, thanks to these PIL functionalities, the BCPIL/Re@HPC/GDL electrode can keep the selectivity toward CO when a higher amount of water is present in the electrolyte than the raw Re@HPC/GDL system. Our results help to understand the development of solid-state ionic liquids for enhanced CO2RR in water-based electrolyte.