The magnetic properties of ultra-small (∼2 nm) δ-(Fe_0.67Mn_0.33)OOH nanoparticles prepared by a microemulsion technique have been investigated by magnetization and ac susceptibility measurements at variable frequency. The results provide evidence of two different magnetic regimes whose onset is identified by two maxima in the zero-field-cooled susceptibility: a large one, centered at ∼150 K (T_mh), and a narrow one at ∼30 K (T_ml). The two temperatures exhibit a different frequency dependence: T_mh follows a Vogel–Fulcher law τ = τ₀ exp[(E_a/k_B)/(T − T₀)], indicating a blocking of weakly interacting nanoparticle moments, whereas T_ml follows a power law τ = τ₀(T_g/T_mν − T_g)^α, suggesting a collective freezing of nanoparticle moments (superspin-glass state). This picture is coherent with the field dependence of T_ml and T_mh and with the temperature dependence of the coercivity, strongly increasing below 30 K.

A microporous carboxylate metal-organic framework MIL-100 Fe was prepared as submicron particles by microwave-assisted hydrothermal synthesis (Fe-MOF-MW). This product was explored, for the first time, for the preparation of polylactic acid (PLA) mixed matrix membranes. The produced MOF was characterised by powder X-ray diffraction (PXRD), environmental scanning electron microscopy (ESEM) as well as by thermogravimetric analysis (TGA) and nitrogen adsorption/desorption. The effect of different Fe-MOF-MW concentrations (0.1 and 0.5 wt%) on the membrane properties and performance were evaluated. These membranes were used in the pervaporation process for the separation of methanol/methyl tert-butyl-ether mixtures at the azeotropic point. The influence of the feed temperature and vacuum pressure on the membrane performance was evaluated and the results were compared with PLA pristine membranes. Moreover, the produced membranes have been characterised in terms of morphology, MOF dispersion in the polymeric membrane matrix, wettability, thickness, mechanical resistance and swelling propensity. The presence of Fe-MOF-MW was found to have a beneficial effect in improving the selectivity of mixed matrix membranes towards methanol at both concentrations. The highest selectivity was obtained for the PLA membranes embedded with 0.5 wt% of Fe-MOF-MW and tested at the temperature of 25 °C and vacuum pressure of 0.09 mbar.