A Zwitterionic Hydrogel-Based Heterogeneous Fenton Catalyst for Water Treatment.

Persistent organic pollutants (POPs), including xenoestrogens and polyfluoroalkyl substances (PFAS), demand urgent global intervention. Fenton oxidation, catalyzed by iron ions, offers a cost-effective means to degrade POPs. However, numerous challenges like acid dependency, catalyst loss, and toxic waste generation hinder practical application. Efforts to create long-lasting heterogeneous Fenton catalysts, capable of simultaneously eliminating acid requirements, sustaining rapid kinetics, and retaining iron efficiently, have been unsuccessful. This study introduces an innovative heterogeneous zwitterionic hydrogel-based Fenton catalyst, surmounting these challenges in a cost-effective and scalable manner. The hydrogel, hosting individually complexed iron ions in a porous scaffold, exhibits substantial effective surface area and kinetics akin to homogeneous Fenton reactions. Complexed ions within the hydrogel can initiate Fenton degradation at neutral pH, eliminating acid additions. Simultaneously, the zwitterionic hydrogel scaffold, chosen for its resistance to Fenton oxidation, forms strong bonds with iron ions, enabling prolonged reuse. Diverging from existing designs, the catalyst proves compatible with UV-Fenton processes and achieves rapid self-regeneration during operation, offering a promising solution for the efficient and scalable degradation of POPs. The study underscores the efficacy of the approach by demonstrating the swift degradation of three significant contaminants-xenoestrogens, pesticides, and PFAS-across multiple cycles at trace concentrations.

Dual-phase microporous polymer nanofilms by interfacial polymerization for ultrafast molecular separation.

Fine-tuning microporosity in polymers with a scalable method has great potential for energy-efficient molecular separations. Here, we report a dual-phase molecular engineering approach to prepare microporous polymer nanofilms through interfacial polymerization. By integrating two micropore-generating units such as a water-soluble Tröger's base diamine (TBD) and a contorted spirobifluorene (SBF) motif, the resultant TBD-SBF polyamide shows an unprecedentedly high surface area. An ultrathin TBD-SBF membrane (~20 nm) exhibits up to 220 times improved solvent permeance with a moderate molecular weight cutoff (~640 g mol-1) compared to the control membrane prepared by conventional chemistry, which outperforms currently reported polymeric membranes. We also highlight the great potential of the SBF-based microporous polyamides for hydrocarbon separations by exploring the isomeric effects of aqueous phase monomers to manipulate microporosity.

Engineering the Polymer-MOF Interface in Microporous Composites to Address Complex Mixture Separations.

Poor interfacial compatibility remains a pressing challenge in the fabrication of high-performance polymer-MOF composites. In response, introducing compatible chemistries such as a carboxylic acid moiety has emerged as a compelling strategy to increase polymer-MOF interactions. In this work, we leveraged compatible functionalities in UiO-66-NH2 and a carboxylic acid-functionalized PIM-1 to fabricate mixed-matrix membranes (MMMs) with improved separation performance compared to PIM-1-based MMMs in industrially relevant conditions. Under pure-gas conditions, PIM-COOH-based MMMs retained selectivity with increasing MOF loading and showed increased permeability due to increased diffusion. The composites were further investigated under industrially relevant conditions, including CO2/N2, CO2/CH4, and H2S/CO2/CH4 mixtures, to elucidate the effects of competitive sorption and plasticization. Incorporation of UiO-66-NH2 in PIM-COOH and PIM-1 mitigated the effects of CO2- and H2S-induced plasticization typically observed in linear polymers. In CO2-based binary mixed-gas tests, all samples showed similar performance as that in pure-gas tests, with minimal competitive sorption contributions associated with the amine functional groups of the MOF. In ternary mixed-gas tests, improved plasticization resistance and interfacial compatibility resulted in PIM-COOH-based MMMs having the highest H2S/CH4 and CO2/CH4 selectivity combinations among the films tested in this study. These findings demonstrate that selecting MOFs and polymers with compatible functional groups is a useful strategy in developing high-performing microporous MMMs that require stability under complex and industrially relevant conditions.

PolyMOF nanoparticles constructed from intrinsically microporous polymer ligand towards scalable composite membranes for CO2 separation.

Integrating different modification strategies into a single step to achieve the desired properties of metal-organic frameworks (MOFs) has been very synthetically challenging, especially in developing advanced MOF/polymer mixed matrix membranes (MMMs). Herein, we report a polymer-MOF (polyMOF) system constructed from a carboxylated polymer with intrinsic microporosity (cPIM-1) ligand. This intrinsically microporous ligand could coordinate with metals, leading to ~100 nm-sized polyMOF nanoparticles. Compared to control MOFs, these polyMOFs exhibit enhanced ultramicroporosity for efficient molecular sieving, and they have better dispersion properties in casting solutions to prepare MMMs. Ultimately, integrating coordination chemistries through the cPIM-1 and polymer-based functionality into porous materials results in polyMOF/PIM-1 MMMs that display excellent CO2 separation performance (surpassing the CO2/N2 and CO2/CH4 upper bounds). In addition to exploring the physicochemical and transport properties of this polyMOF system, scalability has been demonstrated by converting the developed MMM material into large-area (400 cm2) thin-film nanocomposite (TFN) membranes.