Room temperature synthesis of ZIF-8 membranes from seeds anchored in gelatin films for gas separation

Abstract

We developed a new approach to synthesize MOF seeds by directly growing ZIF-8 seeds from zinc hydroxide nanostrands (ZHNs)/gelatin composite thin films. The ZIF-8 seeds were anchored firmly and partially in the gelatin film, which could overcome the poor bonding between the substrate and the MOF layer. Using these seeds, after second growth, a dense and well intergrown ZIF-8/gelatine thin film composite membrane was obtained. The different proportions of gelatin mixed with ZHNs influenced the density of the seeds, accordingly affecting the quality of the final ZIF-8/gelatin membranes. The continuous and well intergrown membranes with a ZIF-8 layer of about 2 μm, exhibited H₂ permeance of 7.68 × 10⁻⁶ mol s⁻¹ Pa⁻¹ m⁻² at room temperature, with ideal selectivities for H₂/CH₄ and H₂/N₂ gases of 14.2 and 9.4, respectively, far beyond the Knudsen selectivity. Similarly, an HKUST-1 seeds/gelatin thin film was also synthesized. This process holds the potential for synthesis of other MOF membranes on various substrates.