Hydrophilic hollow zeolitic imidazolate framework-8 modified ultrafiltration membranes with significantly enhanced water separation properties

Metal-organic frameworks (MOFs) are being intensively investigated for the design of advanced composite membranes, primarily due to their favorable polymer affinity, and highly tunable porous structure and surface properties. However, the development of engineered MOF-based ultrafiltration (UF) membranes for water treatment remains in its infancy. In the present study, hydrophilic hollow zeolitic imidazolate framework-8 (hZIF-8) was meticulously synthesized via surface functionalization-assisted etching approach by using tannic acid (TA), and then incorporated into polysulfone (PSf) casting solution to fabricate novel hybrid UF membranes via phase inversion method. The resultant hZIF-8 not only possessed a highly hydrophilic surface derived from the coated TA but also yielded a unique hollow structure without destroying the intrinsic frameworks. Thanks to the well-tailored surface property and nanostructure of hZIF-8, the obtained PSf/hZIF hybrid UF membranes showed highly improved water permeation (597 L m−2 h−1), which was 2.8 times that of the pristine PSf membrane (210 L m−2 h−1), while well maintaining the rejection property. What's more, the incorporation of hZIF-8 rendered the membrane with enhanced resistance to fouling. These results indicated the great application potential of such MOF/polymer hybrid UF membranes in wastewater treatment and separation in many industrial fields.