Preparation of Ultrathin MOF Membranes for Gas Separation by Orientation Regulation

Purposes Metal-organic framework (MOF) membranes have been extensively studied in recent years owing to their rich porosity as well as their uniform and adjustable pore size. Still, the preparation of ultra-thin and defect-free MOF membranes faces great challenges. Controlling the growth orientation of the MOF membranes helps reduce intergranular defects and optimize membrane thickness. Methods For the first time, an ultra-thin and oriented UTSA-280 MOF membrane is prepared on a porous substrate via a polydopamine (PDA) interface layer-mediation strategy. The PDA layer provides abundant adsorption and anchoring sites for UTSA-280 through multiple interactions with metal ions to facilitate the heterogeneous nucleation and growth of UTSA-280. Furthermore, the nucleation density and growth rate can be controlled through varying PDA deposition amounts to modulate the growth orientation of MOF crystals and membrane thickness. Findings Finally, a (202)-oriented UTSA-280 MOF membrane prepared under optimal conditions with a membrane thickness of 162 nm achieves H2 permeance up to 4 141.8 GPU and H2/CO2 separation selectivity of 18.5, far exceeding the Robeson upper bound in 2008.