Thin-film nanocomposite membranes containing a range of 50-150 nm metal-organic framework (MOF) nanoparticles [ZIF-8, MIL-53(Al), NH2-MIL-53(Al) and MIL-101(Cr)] in a polyamide (PA) thin film layer were synthesized via in situ interfacial polymerization on top of cross-linked polyimide porous supports. MOF nanoparticles were homogeneously dispersed in the organic phase containing trimesoyl chloride prior to the interfacial reaction, and their subsequent presence in the PA layer formed was inferred by a combination of contact angle measurements, FT-IR spectroscopy, SEM, EDX, XPS, and TEM. Membrane performance in organic solvent nanofiltration was evaluated on the basis of methanol (MeOH) and tetrahydrofuran (THF) permeances and rejection of styrene oligomers (PS). The effect of different post-treatments and MOF loadings on the membrane performance was also investigated. MeOH and THF permeance increased when MOFs were embedded into the PA layer, whereas the rejection remained higher than 90% (molecular weight cutoff of less than 232 and 295 g·mol(-1) for MeOH and THF, respectively) in all membranes. Moreover, permeance enhancement increased with increasing pore size and porosity of the MOF used as filler. The incorporation of nanosized MIL-101(Cr), with the largest pore size of 3.4 nm, led to an exceptional increase in permeance, from 1.5 to 3.9 and from 1.7 to 11.1 L·m(-2)·h(-1)·bar(-1) for MeOH/PS and THF/PS, respectively.

Mixed-matrix membranes (MMMs) comprising NH-MIL-53(Al) and Matrimid or 6FDA-DAM have been investigated. The MOF loading has been varied between 5 and 20 wt%, while NH-MIL-53(Al) with three different morphologies: nanoparticles, nanorods and microneedles have been dispersed in Matrimid. The synthesized membranes have been tested in the separation of CO from CH in an equimolar mixture. At 3 bar and 298 K for 8 wt% MOF loading, incorporation of NH-MIL-53(Al) nanoparticles leads to the largest improvement compared to nanorods and microneedles. The incorporation of the best performing filler, NH-MIL-53(Al) nanoparticles, to the highly permeable 6FDA-DAM has a larger effect, and the CO permeability increased up to 85 % with slightly lower selectivities for 20 wt% MOF loading. Specifically, these membranes have a permeability of 660 Barrer with CO/CH separation factor of 28, leading to a performance very close to the Robeson limit of 2008. Furthermore, a new non-destructive technique based on Raman spectroscopy mapping is introduced to assess the homogeneity of the filler dispersion in the polymer matrix. The MOF contribution can be calculated by modelling the spectra. The determined homogeneity of the MOF filler distribution in the polymer is confirmed by FIB-SEM analysis.

Silica-(ZIF-8) core-shell spheres with tuneable ordered meso-microporosity have been synthesized, showing that the hydrophobic micropore ZIF-8 shell controls the access of guest molecules into the hydrophilic silica mesoporous structure.

MOF nanoparticles of MIL-68(Al), MIL-101(Cr) and ZIF-11 for thin film nanocomposite organic solvent nanofiltration.

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BACKGROUND: Pervaporation (PV) is a prospective industrial process for the separation of liquid mixtures such as azeotropic and close-boiling point. PV efficiency depends mainly on the properties of the membrane used. Hence, designing a membrane structure with high permeation rate and separation factor is an important issue.

This work reports the fabrication and characterization of Langmuir-Blodgett films of nanoparticles (size 51 ± 10 nm) of the metal organic framework MIL-101(Cr). LB film characterization by SEM, UV-vis, GIXRD and QCM has shown that the addition of 1 wt.% of behenic acid to MOF dispersion allows obtaining dense monolayers at the airwater interface that can be deposited onto solid substrates of different nature with transfer ratios close to 1. Moreover, a QCM-based setup has been built and used for the first time to measure CO 2 adsorption isotherms at 303 K on MOF LB films, proving that LB films with MOF masses between 1.2 (1 layer) and 2.3 (2 layers) micrograms can be used to obtain accurate adsorption values at 100 kPa, similar to those obtained by conventional adsorption methods that require much larger MOF quantities (tens of milligrams).3