Contra-diffusion synthesis of metal-organic framework separation membranes: A review

• MOF membranes offer great potential for various separation processes. • Contra-diffusion synthesis is applied for MOF preparation. • Contra-diffusion synthesis gives defect-free membranes due to the self-healing process. • The critical challenges and future research directions are also discussed. Metal-organic framework (MOF) membranes offer great potential for various separation processes. Although extensive efforts have been devoted to preparing MOF-based membranes, the fabrication of defect-free MOF membranes remains an ongoing challenge. Contra-diffusion synthesis is a synthetic approach where different synthesis solutions are separated by a porous membrane support and crystallization takes place on the interfaces through solution contra-diffusion. Herein, recent advances in contra-diffusion synthesis of MOF membranes are reviewed in detail. The critical challenges and future research directions are also discussed.