In situ assembled zeolite imidazolate framework nanocrystals hybrid thin film nanocomposite membranes for brackish water desalination

Metal organic frameworks (MOFs) can provide additional angstrom-scale channels for unimpeded transport of water, thus various attempts are increasingly being made to effectively embed them into polyamide (PA) nanofilms. Conferring the inherent advantages of MOFs nanofillers to the thin-film nanocomposite membranes (TFN) remains challenging. Here, a novel coordination-driven in-situ self-assembly strategy is proposed for fabricating ZIF-8 nanocrystals hybrid TFN membrane with enhanced remarkably desalination performance. In this way, ZIF-8 nanocrystals are evenly in-situ grown onto the porous ultrafiltration substrate induced by poly(sodium 4-styrenesulfonate) (PSS)-metal ions complex interlayer, then are wrapped in-situ into PA active layer without agglomeration and defects via interfacial polymerization (IP) process. Benefiting from the homogeneous incorporation of ZIF-8 nanofillers, the optimal TFN-ZIF-8 membrane evinces a water flux of nearly four times that of the traditional TFC membrane, while remaining an improved NaCl rejection (∼99.03%). Moreover, the in-situ assembled ZIF-8 nanocrystals layer can tune surface morphology to evolve from typical leaf-like structures to smooth nodular features. Consequently, the significantly decreased surface roughness and increased surface hydrophilicity endow the TFN-ZIF-8 membrane with superior antifouling performance. In addition, it is universal for other MOFs nanofillers (ZIF-67 and HKUST-1) to fabricate the highly-permeable hybrid TFN membranes. Therefore, this work promotes the advancement of competent TFN membranes to overcome the current bottleneck for brackish water desalination.