Tailoring the separation performance of ZIF-based mixed matrix membranes by MOF-matrix interfacial compatibilization

Ultrasmall Functionalized UiO-66 Nanoparticle/Polymer Pebax 1657 Thin-Film Nanocomposite Membranes for Optimal CO2 Separation

Ultrasmall 4 to 6 nm nanoparticles of the metal-organic framework (MOF) UiO-66 (University of Oslo-66) were successfully prepared and embedded into the polymer Pebax 1657 to fabricate thin-film nanocomposite (TFN) membranes for CO2/N2 and CO2/CH4 separations. Furthermore, it has been demonstrated that ligand functionalization with amino (-NH2) and nitro (-NO2) groups significantly enhances the gas separation performance of the membranes. For CO2/N2 separation, 7.5 wt % UiO-66-NH2 nanoparticles provided a 53% improvement in CO2 permeance over the pristine membrane (from 181 to 277 GPU). Regarding the CO2/N2 selectivity, the membranes prepared with 5 wt % UiO-66-NO2 nanoparticles provided an increment of 17% over the membrane without the MOF (from 43.5 to 51.0). However, the CO2 permeance of this membrane dropped to 155 GPU. The addition of 10 wt % ZIF-94 particles with an average particle size of ∼45 nm into the 5 wt % UiO-66-NO2 membrane allowed to increase the CO2 permeance to 192 GPU while maintaining the CO2/N2 selectivity at ca. 51 due to the synergistic interaction between the MOFs and the polymer matrix provided by the hydrophilic nature of ZIF-94. In the case of CO2/CH4 separation, the 7.5 wt % UiO-66-NH2 membrane exhibited the best performance with an increase of the CO2 permeance from 201 to 245 GPU.

Durable and recyclable MOF@polycaprolactone mixed-matrix membranes with hierarchical porosity for wastewater treatment

With the fast-growing global water crisis, the development of novel technologies for water remediation and reuse is crucial. Industrial wastewater especially contains various toxic pollutants that pose an additional threat to the environment; thus, efficient removal of such contaminants can ensure safe reprocessing of industrial wastewater, thereby alleviating the demand for fresh water. Herein, we describe a novel and efficient approach for preparing porous polycaprolactone (PCL) membranes with a hierarchical architecture via a simple solvent/non-solvent methodology. A mixed-matrix membrane (MMM) was further constructed utilizing an amine-functionalized metal-organic framework as the sorbent filler nanoparticles and PCL as the polymer support matrix (MOF@PCL) for wastewater treatment applications. The MOF@PCL MMM demonstrated homogeneous morphology as well as exceptional performance towards the removal of both cationic (methylene blue, MB) and anionic (methyl orange, MO) organic dyes, where the maximum adsorption capacities reached 309 mg g-1 and 208 mg g-1, respectively. Kinetic and thermodynamic investigations revealed that the adsorption process was endothermic with a fast intraparticle diffusion rate constant. The MOF@PCL MMM also displayed excellent mechanical stability and recyclability, where the removal efficiency was maintained after 10 cycles.

ZIF-8 @polycarbonate nanocomposite membranes for improved permeability and selectivity for hydrogen gas

Through this work, we are reporting high-performance ZIF-8 @polycarbonate nanocomposite membranes with satisfactory structural stability for improving the gas separation performance. ZIF-8 nanoparticles were synthesised using the wet chemical route with cubic morphology and controlled size using CTAB as a surfactant. The membranes were prepared using the solution casting method by adding ZIF-8 filler at various concentrations. The synthesised filler material and MMMs were characterised through X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and RAMAN spectroscopy techniques. The gas separation measurements were taken using H2, CO2, and N2 gas in the purest form. The SEM results confirm the formation of spherulite-like morphology with the addition of ZIF-8 due to the crystallisation of the polymer, which increased the membrane's free volume and opened up additional pathways for the transportation of the gas molecules. The gas separation results confirmed that the 15 wt% ZIF-8/PC nanocomposite membrane showed the maximum H2 permeability of 180,970 barrer with an increment of 316.03%, while H2/CO2 and H2/N2 selectivity showed the increments of 89.43% and 103.64%, respectively. Therefore, this PC/ZIF-8 system seems to be a promising approach to developing new H2 selective membranes with high gas permeability and gas selectivity values.