Isomeric Separation of C6 Alkanes via Organic Solvent Reverse Osmosis with Covalent Organic Framework Membranes

Membrane separation represents cutting-edge technology for the isomeric separation of C6 alkanes in the petrochemical sector. However, it remains challenging to design membranes with sub-0.1 nm resolution that can effectively discriminate between C6 alkane isomers. In this study, we report a molecularly selective, ultramicroporous covalent organic framework (COF) membrane featuring an accessible pore size of ∼4.5 Å for the isomeric separation of C6 alkanes. High permeance of 2.56 kg m^–2 h^–1 bar^–1 together with a high selectivity of 70.9 are achieved for a binary separation of linear n-hexane (nHEX) and branched 2,3-dimethylbutane (23DMB) through organic solvent reverse osmosis (OSRO). Notably, the research octane number (RON) of a five-component C6 alkane mixture can be effectively improved from 67.7 to 92.8 through a continuous separation using the COF membrane. The exceptional performance of the COF membrane suggests a new design of next-generation molecularly selective membranes toward efficient isomeric separation.