Facile synthesis of a continuous thin Cu(bipy)2(SiF6) membrane with selectivity towards hydrogen

Abstract

Cu(bipy)₂(SiF₆) is a highly porous metal–organic framework (MOF) and represents a prototypal “pillared sheet” platform offering opportunities to control the pore sizes. Its structural features, low cost and facile synthesis make it a great candidate to fabricate membranes for gas separation. The key to obtaining thin, continuous Cu(bipy)₂(SiF₆) membranes is to control the Cu(bipy)₂(SiF₆) crystal growth and enhance the binding between membrane and substrate. Here we explored a new route by direct synthesis and successfully obtained a continuous thin Cu(bipy)₂(SiF₆) membrane on a macroporous glass-frit disk with high robustness. It is speculated that the SiF₆²⁻ used to construct the Cu(bipy)₂(SiF₆) membrane came from the fluorinated substrate. The Cu(bipy)₂(SiF₆) membrane shows the separation factors of H₂–CO₂, H₂–CH₄ and H₂–N₂ are 8.0, 7.5, and 6.8 respectively at 293 K and 1 bar with H₂ permeance of 2.7 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ as well as high thermal stability. We expect to explore more membranes of Cu(bipy)₂(SiF₆) analogues with tuneable pore sizes using this route and to obtain membranes with higher gas separation performance.