A Highly Selective Supramolecule Array Membrane Made of Zero-Dimensional Molecules for Gas Separation

We orderly assembled zero-dimensional 2-methylimidazole (mim) molecules into unprecedented supramolecule array membranes (SAMs) through solvent-free vapor processing, realizing the intermolecular spacing of mim at ca. 0.30 nm available as size-sieving channels for distinguishing the tiny difference between H₂ (kinetic diameter: 0.289 nm) and CO₂ (kinetic diameter: 0.33 nm). The highly oriented and dense membranes yield a separation factor above 3600 for equimolar H₂ /CO₂ mixtures, which is one order of magnitude higher than those of the state-of-the-art membranes defining 2017's upper bound for H₂ /CO₂ separation. These SAMs define a new benchmark for molecular sieve membranes and are of paramount importance to precombustion carbon capture. Given the range of supramolecules, we anticipate SAMs with variable intermolecular channels could be applied in diversified separations that are prevalent in chemical processes.