Swelling polymer-regulated green synthesis of flexible ZIF-8 membrane

Metal-organic framework (MOF)-based membranes are promising for the development of high flux separation applications while maintaining high selectivities. Since pure MOF membranes typically suffer from brittleness, the fabrication of flexible MOF membranes with minimal defects and good mechanical strength is valuable. Herein, we report a swelling polymer-regulated method for the in situ green synthesis of a flexible zeolitic imidazolate framework-8 (ZIF-8) membrane for gas separation. By applying reactant solutions with different solvents in the contra-diffusion process, ZIF-8 particles were gradually grown with binding to alginate polymers. Moreover, the directional swelling of the composite layer allowed the selective layer to grow further into the pores of the substrate. This membrane demonstrated good structural integrity and mechanical stability whilst achieving an H₂ permeance of 6.81 ​× ​10⁻⁷ ​mol ​m⁻² ​s⁻¹·pa⁻¹ and an ideal H₂/CH₄ selectivity of 24, which was able to retain its gas separation performance after 10 mild bends. This approach thus shows great potential for the further development of other flexible MOF membranes.