Ortho/meta/para-xylene are precursors to appliances used in everyday life, with para-xylene (PX) heavily used in the production of plastics. The current industrial separation of these isomers is a highly energy demanding process owing to their similar boiling points. Porous materials such as polymers, metal-organic-frameworks and, more recently, molecular cages can be developed into membranes which can selectively separate these isomers under far less energy-intensive conditions. This project will focus mainly on the development of porous organic cages for their use in molecular separations to answer the question: How can organic porous materials reduce the emissions from industrial processes? To begin to approach the solution, a custom molecular separation rig will first be designed and built before the design and synthesis of cage molecules which will be implemented into membranes for use in the separation rig. These membranes will not be limited to only those formed from purely porous organic cages but also combined with polymers to form mixed-matrix membranes or treated to form carbon molecular sieves. Membrane performance will then be correlated with the structural and chemical characterisation to better understand the selectivity-structure relationship with a potential long-term aim to scale-up beyond laboratory size.