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.