Mixed-matrix or polymeric organic solvent resistant nanofiltration (OSN) membranes with high solvent permeability and selectivity will have broad applications in chemical and pharmaceutical industries. Nano-porous metal-organic frameworks (MOFs) with tunable pore sizes and ligand properties have generated tremendous interest due to their many possible applications. Here MOFs are embedded in polymer matrices to make mixed matrix membranes (MMM) with enhanced selectivity and permeability. Crystalline Cu(I) and Cu(II) MOFs that can selectively interact with targeted aromatic compounds are synthesized with particle sizes ranging from nanometers (nm) to micrometers (mm). MMMs containing these MOFs were explored for affinity based hydrocarbon separations. Quantum mechanical calculations coupled with classical simulations were conducted to elucidate its selectivity based on the specific solvent-MOF interactions. Besides affinity based MMMs, size based OSN membranes using high free volume glassy perfluoropolymer were investigated. The fractional free volumes (FFV) and pore size distributions of various perfluoropolymeric membranes with different ratios of cyclic to linear monomer units were determined using classical molecular dynamics (MD) simulations.