The search for new and more energy-efficient solutions with natural fluids has become a clear countermeasure for mitigating the carbon footprint of air conditioning and refrigerating systems. In the absorption field, specifically in liquid desiccant air conditioning systems, the application of internal cooling in gas-liquid contactors is limited due to the corrosion property of commonly used liquid desiccants. Internally cooled/heated liquid desiccant systems have better heat and mass transfer performance compared to adiabatic systems but mathematical modeling becomes more complicated. In this study, experiments and simulations were carried out to evaluate the performance of an internally cooled/heated liquid desiccant air conditioning system using a novel ionic liquid. This innovative solution became possible due to the compatibility, in terms of corrosion, of the newly developed ionic liquid with aluminum. The validated mathematical model can be used to conduct parametric and optimization studies for the internally cooled/heated liquid desiccant air conditioning system.