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.