Advances in metal-organic frameworks for membrane distillation: A review

In recent years, Membrane Distillation (MD), as a thermally driven separation technology based on microporous hydrophobic membranes, has been widely used in the fields of seawater desalination and brine concentration in salt lakes due to its advantages of high salt discharge rate, high permeate flux, high energy efficiency and compatibility with renewable energy sources. Metal-organic frameworks (MOFs), as a class of porous materials with high specific surface area, tunable pore size, and multifunctional active sites, provide a new strategy for MD membranes to mitigate temperature polarization and concentration polarization, improve membrane stability, and enhance excellent catalytic/adsorption functions with their unique structural properties. This paper describes the basic principles and problems of MD, comparatively analyzes the applicability of six types of MOF materials, UIO, ZIF, MIL, HKUST, AlFu and CAU, in MD. Discusses different synthesis methods and modification strategies of MOF-based membranes, including phase transformation, electrospinning, in situ growth, and vacuum filtration, etc. The pathway of MOF to optimize the performance of MD through the mechanisms of pore size sieving, hydrophobic modification and pollutant adsorption was analyzed. Finally, the future development of MOF membranes in the direction of material selection, membrane structure design and modification, and integration process is envisioned to provide theoretical guidance and technical reference for the breakthrough of the bottleneck of MD technology.