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This study presents a sustainable microwave-assisted synthesis, based on the use of acetone and a water/acetic acid mixture instead of typical harmful DMF, to fabricate Zr-metal–organic frameworks (MOFs) UiO-66 and MOF-808 as fillers in a PIM-1 matrix for gas separation application. The mixed matrix membranes (MMMs) were prepared with varying loadings (2.5–10 wt%) of MOFs. The physicochemical properties (1H NMR, FTIR, XRD, N2 adsorption, TGA and SEM) of the resulting PIM-1, MOFs and MMMs were analyzed. The CO2/CH4 separation performance and membrane aging characteristics of the MMMs were evaluated. The incorporation of MOF fillers significantly improved CO2 permeability and CO2/CH4 selectivity, attributed to their CO2-philicity and narrow pore size (UiO-66 ≈ 0.6 nm and MOF-808 ≈ 1.8 nm). The MMMs with higher filler loadings (7.5 and 10 wt%) exhibited the most favorable separation performance. Due to the better crystallinity and textural properties, MOF-808 produced the best separation results at 10 wt% filler loading (a CO2/CH4 separation selectivity of 16.2 at 9090 Barrer of CO2 permeability). Aging led to a decrease in CO2 permeability but a slight increase in CO2/CH4 selectivity for all MMMs. Overall, the study highlights the potential of PIM-1/UiO-66 and PIM-1/MOF-808 MMMs as efficient materials for (CO2/CH4) separation comparing with the pristine PIM-1.

Some copper-based metal–organic frameworks show promise for use as electrocatalysts because they allow for an electrode configuration in which copper species with redox and electron-conducting properties are immobilized in a three-dimensional arrangement. This work shows that the synthesis of copper terephthalates (Cu-BDCs) can lead to rigid structures of the copper hydroxyterephthalate-type or flexible structures that are isoreticular to the MOF-2 type, depending solely on the synthesis route. Here, a detailed analysis of the syntheses of the crystals is carried out employing protocols with different solvents as well as conventional or microwave-assisted solvothermal methods. All solids were fully characterized by a combination of characterization techniques, such as FE-SEM, T-XRD, TGA, and FTIR, and their electrochemical redox responses were also evaluated by cyclic voltammetry. A correlation between the Cu-BDCs structures and their electrochemical behaviors was established and a new version of an electroactive copper hydroxyterephthalate was synthesized by a microwave method in 3 h with a dimethylformamide-free protocol. This Cu-BDC was obtained as dispersed nanoflakes with a high amount of copper sites and the capacity to be reversibly electroreduced-oxidized and showed catalytic activity in the oxygen reduction reaction (ORR).

[EN] Metal-organic frameworks (MOFs) with redox properties are potentially good candidates as noble-metal free electrocatalysts due to their high specific surface area, uniform pore size and shape, and high dispersion of redox centers. Copper-based MOFs are particularly interesting as oxygen reduction electrocatalysts due to the well-known bio-affinity of this element towards oxygen in oxygen-reducing proteins. In this line, the metal–organic framework Cu-MOF-74, which has open metal sites in its 3D structure has not been studied up to date as electrocatalyst for the oxygen reduction reaction (ORR). This work reports an exhaustive electrochemical analysis of nanocrystalline Cu-MOF-74, for assessing its electrochemical behavior and electrocatalytic performance for the ORR. Nanocrystals of Cu-MOF-74 (about 40 nm in size) with intercrystal mesoporosity and high surface area (>1000 mg) were synthesized by a previously reported procedure. The study of this material supported on glassy carbon (GC) rotating disk electrodes allowed to prove its good stability in neutral electrolytic medium and an efficient connectivity of the open Cu centers with redox ability. Moreover, GC/Cu-MOF-74 electrodes were capable to efficient electro-reduce dissolved oxygen to water at overpotentials higher than −0.62 V, fully preserving the framework integrity after long-time assays. It was also verified that this four-electron process is mediated by the reduction of Cu centers exposed at the inner walls of the MOF pores, involving electro-adsorbed oxygenated intermediates. The location of the active sites inside the deep structural nanopores strongly affects the mass transport properties and is detrimental for the whole performance as ORR electrocatalyst. Thus, while the results reported here provide new evidences on the redox and electrocatalytic behavior of nanocrystalline Cu-MOF-74, it is clear that its configuration must be rethought in order to attain an acceptable ORR performance.

The physicochemical modification of Metal‐Organic Frameworks (MOFs) is a current challenge in the search to improve their performance in different technological applications. In this work we analyze the post‐synthetic modification of ZIF‐8 crystals and films through a simple and clean treatment that involves the exposure to a UV lamp under environmental conditions. It is demonstrated that a short treatment alters the MOF structure and chemistry, providing a modified ZIF‐8 due to partial disconnections of its structure which increase the amount of terminal surface species such as Zn−OH and −C=N‐H, but without compromising the overall MOF structure, specific surface area or thermal stability. Additionally, it leads to changes in several properties of the ZIF‐8, such as its capacity to accumulate charge through pseudocapacitive processes, its interaction with nitric oxide and its light absorption behavior. This strategy of modifying ZIF‐8 without the use of chemicals through a gentle disconnection of its own structure could open new perspectives of post‐functionalization of crystals and films of ZIF‐8 to be used in a wide range of applications.

[EN] The application of Metal-Organic Frameworks (MOFs) in gas phase heterogeneous catalysis is still not widely spread because of their limited stability under reaction conditions. Obtaining stable acidic MOFs to be used in reactions that demand strong acid sites remains a challenge up to the present time. In this work, it is shown that nanocrystals of Zirconium MOF UiO-66 can be conveniently and easily functionalized through a simple one-pot synthetic approach, i.e. the direct treatment of UiO-66 with ammonium sulfate followed by an adequate thermal treatment, giving rise to a highly acidic and thermally stable material (named as S-UiO-66). This material can act as catalyst in the gas phase isobutene dimerization demonstrating high catalytic activity at moderate temperatures while maintaining the structural integrity of the MOF after several catalytic evaluations and/or after reuse cycles. The S-UiO-66 material represents a novel alternative in the search of robust MOF-based catalysts to be applied in gas phase heterogeneous catalytic reactions that demand strong acid sites.