Precise assembly of a zeolite imidazolate framework on polypropylene support for the fabrication of thin film nanocomposite reverse osmosis membrane

Polypropylene (PP) has been widely used in the fields of lithium battery separators, proton exchange membranes, membrane bioreactors and polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membranes owing to its excellent mechanical strength, chemical durability and low cost. Nevertheless, its inherent strong hydrophobicity and low surface porosity severely limit its in-depth development in the field of polyamide TFC membranes. Herein, we propose a general strategy for the precise assembly of ZIF-8 nanoparticles on PP support for the fabrication of RO membrane. By this method, position induced nanoporous surface (PINS) was introduced via in-situ synthesis of ZIF-8 assisted by diazonium-induced anchoring process (DIAP) on PP support, and it would achieve precise repair of non-porous regions of PP support, thereby increasing its surface porosity and hydmphilicity of PP support. Subsequently, a high-performance ZIF-8 hybrid reverse osmosis (HPP-ZIF-8-RO) membrane was fabricated by conventional interfacial polymerization (IP) on modified commercialized PP support for the first time. The optimal rejection of HPP-ZIF-8-RO for NaCl is similar to 99%, and the water flux is up to 50 kg m(-2) h(-1) under the operating pressure of 1.55 MPa. In addition, the HPP-ZIF-8-RO membrane has a superior chemical stability after the solvent resistance test. To prove the university of DIAP and PINS, we have successfully fabricated other types of HPP-MOF-RO (HPP-ZIF-67-RO, HPP-HKUST-1-RO) which also show enhanced desalination performance. Hence, DIAP and PINS could provide a convenient and versatile method for precise repairing the defect area of the hydrophobic porous substrates.