No abstract

Thin-film nanocomposite (TFN) membranes prepared by embedding nanofillers into an ultrathin polyamide layer have paved the way toward developing high-performance reverse osmosis (RO) desalination membranes. Scale-up production of TFN membranes is still a challenging issue, however, since previous studies have merely followed the same fabrication method for conventional RO membranes. Herein, we introduced a novel preparation method for TFN membranes using spray-assisted nanofiller predeposition to circumvent the limitations in conventional methods. The precise control of nanofiller (ZIF-8) loading was possible by simply varying the spraying ZIF-8 concentration. Most importantly, TFN membranes prepared by both spray and conventional method showed similar RO performance, while the spray method only requires ∼100 times the minimal amount of ZIF-8 with the most unprecedentedly short deposition time (<1 min) ever reported. Our results revealed that the spray method would be promising for the scale-up production of TFN membranes in terms of cost, time, and controllability.

No abstract

Metal−organic frameworks (MOFs) have been extensively studied as promising nanofillers in developing high-performance polymer nanocomposite membranes (PNMs) for efficient water/ion separation applications. However, given the ambiguous role of embedded MOFs, achieving simultaneous improvement in both water permeability and water/ion selectivity of PNMs remains challenging. Here, we elucidates fundamental water and ion transport properties of MOF/PNMs to better understand the role of embedded MOFs in polymer matrices. We prepared freestanding PNMs consisting of a cross-linked poly(ethylene glycol) (XPEG)-based hydrogel and nanoporous zeolitic imidazole framework-8 (ZIF-8) exhibiting high diffusivity selectivity. The transport studies and material characterizations, especially with Raman mapping analysis showing a homogeneous distribution of permeating water molecules throughout ZIF-8/ XPEG PNM, revealed that the incorporated ZIF-8 acts as an additional waterpermselective channel inside the polymeric matrix, which leads to an unusual "reverse-selective" ion transport behavior. Ultimately, 20 wt % of ZIF-8 loading could significantly enhance both water permeability (∼240%) and water/NaCl selectivity (∼160%) compared to a pure polymer membrane by overcoming the conventional permeability−selectivity trade-off limitation. Our finding provides new insights for developing advanced PNMs for water/ion separation.

Advanced modeling and experimental characterization tools were coupled to gain an unprecedented in-depth characterization of the interface formed when a hybrid porous solid ZIF-8 is incorporated as filler onto an amine-functionalized graphene oxide (GO) matrix. As a preliminary stage, an aminopyridine-functionalized GO was synthesized, and a realistic atomistic model was computationally built integrating their structural and chemical features deduced from X-ray photoelectron spectroscopy and X-ray diffraction experiments. An atomistic representation of the ZIF-8/functionalized GO interface was further simulated and carefully analyzed in terms of the nature and the strength of interactions between the two components and the GO conformation with a special emphasis on the impact of the functionalization. It was revealed that grafting the aminopyridine function at the GO significantly enhances the interactions with the terminal functions present at the MOF interface associated with an in-depth penetration of the functionalized GO into the pockets of the ZIF-8. The so-predicted high compatibility between the two components was then supported by Infrared experiments collected on the prepared composite. Complementary transmission electron microscopy experiments further revealed a homogeneous dispersion of the ZIF-8 nanoparticles into the GO matrix with the absence of MOF agglomeration and mechanical testing evidenced a significant enhancement of the tensile strength for the corresponding composite. This fundamental exploration unambiguously demonstrates the key role played by the GO functionalization to achieve optimal interfacial MOF/GO properties, and this opens promising perspectives for processing thin films required for future applications.