In this research, I focus on the physical vapor deposition of small molecules onto the polydimethylsiloxane (PDMS) surface to enhance the selectivity of CO₂/N₂ gas separation. The idea is that specific small molecules with chosen functional groups will provide a suitable CO₂ affinity to improve the CO₂ gas transport through the membrane. Using physical vapor deposition is a novel approach in this direction. The deposition from the vapor phase enables the uniform coating of the membrane surface with precise nanoscale thickness control. It also prevents negative effects that occur when exposing the polymer to organic solvents during wet chemistry approaches.