Utilising photocatalysis as a mild activation method holds great promise for CO2 utilisation, aligning with the objective of generating C1-building blocks like CO and CH4 to advance strategies for a circular carbon economy. Highly efficient CO2 reduction catalysts can be synergistically employed with cooperative media, such as imidazole-based ionic liquids (IL), which can physisorb and chemisorb large amounts of CO2. The chemisorption of CO2 in ionic liquids leads to the formation of ionic liquid-CO2 adducts, facilitating the bending of the CO2 bond angle and thereby pre-activating the molecule. [1–3] Our study systematically explores the impact of imidazolium-based ionic liquids as cooperative media in homogeneous photocatalytic CO2 reduction, employing a ruthenium sensitiser and a rhenium catalyst in various solvents with a particular focus on the role of counter-anion properties. The integration of these imidazolium-based ionic liquids into heterogeneous systems, such as TiO2-based composites, is particularly intriguing. This approach could enhance the system's CO2 absorption capacity, providing pre-activated CO2 in close proximity to single-site reaction centres and enabling gas-phase reactions. Our investigation focuses on the influence of ionic liquids on photocatalytic rhenium single-site catalysis in both liquid and gas phases, utilising the supported ionic liquids concept in conjunction with photoactive supports and single-site catalyst Re(bpy)(CO)3Cl selective for CO reduction.