Heat-driven molecule gatekeepers in MOF membrane for record-high H2 selectivity

Hydrogen/carbon dioxide (H2/CO2) separation for sustainable energy is in desperate need of reliable membranes at high temperatures. Molecular sieve membranes take their nanopores to differentiate sizes between H2 and CO2 but have compromised at a marked loss of selectivity at high temperatures owing to diffusion activation of CO2. 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 CO2 and restitute with cool conditions. The H2/CO2 selectivity was improved by an order of magnitude at 513 kelvin (K) relative to that at the ambient temperature.

Automated summary

Reliable membranes for hydrogen/carbon dioxide (H2/CO2) separation at high temperatures are urgently needed for sustainable energy. In this study, molecule gatekeepers locked in metal-organic framework membranes were used to address the challenge. Ab initio calculations and in situ characterizations showed that the molecule gatekeepers dynamically reshaped the sieving apertures to be tightly selective for CO2 at high temperatures and restored under cooler conditions, resulting in a significant improvement in H2/CO2 selectivity.