Metal-organic framework nanosheets as building blocks for molecular sieving membranes

TLDR: The preparation of 1-nanometer-thick sheets with large lateral area and high crystallinity from layered MOFs used as building blocks for ultrathin molecular sieve membranes, which achieve hydrogen gas permeance of up to several thousand gas permeation units (GPUs) with H2/CO2 selectivity greater than 200.

Abstract: Layered metal-organic frameworks would be a diverse source of crystalline sheets with nanometer thickness for molecular sieving if they could be exfoliated, but there is a challenge in retaining the morphological and structural integrity. We report the preparation of 1-nanometer-thick sheets with large lateral area and high crystallinity from layered MOFs. They are used as building blocks for ultrathin molecular sieve membranes, which achieve hydrogen gas (H2) permeance of up to several thousand gas permeation units (GPUs) with H2/CO2 selectivity greater than 200. We found an unusual proportional relationship between H2 permeance and H2 selectivity for the membranes, and achieved a simultaneous increase in both permeance and selectivity by suppressing lamellar stacking of the nanosheets.