Heat-driven molecule gatekeepers in MOF membrane for record-high H(2) selectivity

Hydrogen/carbon dioxide (H(2)/CO(2)) separation for sustainable energy is in desperate need of reliable membranes at high temperatures. Molecular sieve membranes take their nanopores to differentiate sizes between H(2) and CO(2) but have compromised at a marked loss of selectivity at high temperatures owing to diffusion activation of CO(2). We used molecule gatekeepers that were locked in the cavities of the metal-organic framework membrane to meet this challenge. Ab initio calculations and in situ characterizations demonstrate that the molecule gatekeepers make a notable move at high temperatures to dynamically reshape the sieving apertures as being extremely tight for CO(2) and restitute with cool conditions. The H(2)/CO(2) selectivity was improved by an order of magnitude at 513 kelvin (K) relative to that at the ambient temperature.