Amine-Rich Molecular Nodule-Assembled Membrane Having 5 Angstrom Channels for CO₂/N₂ Separation

Porous organic cages (POCs) with abundant porosity and interconnected cavities have garnered significant research attention as a distinct class of porous materials due to their potential applications in gas sorption and separation. However, the ordered arrangement of POCs to eliminate inter-cage defects remains challenging in the assembly of molecular-selective membranes, which greatly hinders the effectiveness of pore sieving. Here, amine-rich molecular nodules (AMNs) are created by reduction of the porous organic cage CC2, in which the spatial structure incurs a vertex collapse into the interior of the original tetrahedral structure, which eliminates the large window of CC2. By an interfacial reaction with terephthaloyl chloride, the AMNs assemble into a cross-linked topological network having angstrom-scale channels for selective CO2/N-2 separation. The AMN-assembled membrane displays a high CO2 permeance of 752 GPU, a CO2/N-2 selectivity of 67 at 1 bar, as well as high-pressure resistance, operational stability, and scalable manufacture potential, which provides a cost-effective and practical solution for developing membranes for capturing CO2 from industrial flue gas.