We report the preparation and electrocatalytic performance of silver-containing gas diffusion electrodes (GDEs) derived from a silver coordination polymer (Ag-CP). Layer-by-layer growth of the Ag-CP onto porous supports was applied to control Ag loading. Subsequent electro-decomposition of the Ag-CP resulted in highly selective and efficient CO₂-to-CO GDEs in aqueous CO₂ electroreduction. Afterward, the metal-organic framework (MOF)-mediated approach was transferred to a gas-fed flow electrolyzer for high current density tests. The in situ formed GDE, with a low silver loading of 0.2 mg cm^-2, showed a peak performance of j_CO ≈ 385 mA cm^-2 at around -1.0 V vs RHE and stable operation with high FE_CO (>96%) at j_Total = 300 mA cm^-2 over a 4 h run. These results demonstrate that the MOF-mediated approach offers a facile route for manufacturing uniformly dispersed Ag catalysts for CO₂ electrochemical reduction by eliminating ill-defined deposition steps (drop-casting, etc.) while allowing control of the catalyst structure through self-assembly.

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During the last decade, the synthesis and application of metal-organic framework (MOF) nanosheets has received growing interest, showing unique performances for different technological applications. Despite the potential of this type of nanolamellar materials, the synthetic routes developed so far are restricted to MOFs possessing layered structures, limiting further development in this field. Here, a bottom-up surfactant-assisted synthetic approach is presented for the fabrication of nanosheets of various nonlayered MOFs, broadening the scope of MOF nanosheets application. Surfactant-assisted preorganization of the metallic precursor prior to MOF synthesis enables the manufacture of nonlayered Al-containing MOF lamellae. These MOF nanosheets are shown to exhibit a superior performance over other crystal morphologies for both chemical sensing and gas separation. As revealed by electron microscopy and diffraction, this superior performance arises from the shorter diffusion pathway in the MOF nanosheets, whose 1D channels are oriented along the shortest particle dimension.

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Zeolites with DDR (Sigma-1 and ZSM-58) and CHA (SSZ-13) topology were synthesized by seed assisted and direct hydrothermal synthesis in order to investigate the effects of fast crystal growth on catalytic performance. Application of small amount of seeds (0.1% wt) significantly reduced synthesis time of all the studied zeolites. XRD and NH₃-TPD analyses did not reveal any difference in crystallinity and acidity. On the other hand, IR spectroscopy clearly demonstrates the presence of multiple defects, internal silanols (3729 cm^-1) and silanol nests (3400 cm^-1), as a result of accelerated crystal growth kinetics. Comparison of catalytic properties in the dimethyl ether to olefins (DMTO) reaction at 400°C and 450°C revealed that, despite smaller crystal sizes, zeolites prepared by secondary growth display shorter lifetimes due to faster coking rates, the latter being a result of silanols promoting hydrogen transfer reactions. Fluoride treatment of CHA removed silanols and prolonged its lifetime. This work highlights the importance of zeolite quality for catalytic application and the necessity to optimize current synthetic protocols based on secondary growth.

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A systematic study of the effect of physicochemical properties affecting catalyst deactivation, overall olefin selectivity and ethylene/propylene ratio during the methanol-to-olefins (MTO) reaction is presented for two zeolites with the DDR topology, namely Sigma-1 and ZSM-58. Both catalysts show high selectivity towards light olefins and completely suppress the formation of hydrocarbons bigger than C4, with selectivity to ethane not exceeding 1% and some traces of propane. By applying seeded growth approach, a series of Sigma-1 zeolites with tunable crystal size and acidity was synthesized. For this series the highest methanol throughput at 450 °C before deactivation was found for crystals 0.5 μm in size with an acidity corresponding to 0.5 Al atoms per zeolite cage, and a selectivity to ethylene and propylene reaching 90%. Comparison between ZSM-58 and Sigma-1 catalysts with similar morphologies and acidity under the same reaction conditions revealed a three times higher throughput of methanol in case of ZSM-58. The analysis of functional surface groups, assessed through FT-IR, revealed the presence of silanol defects in Sigma-1 responsible for faster catalyst deactivation. These silanol defects can be selectively removed (confirmed by FT-IR) from the zeolite framework by applying a mild treatment in presence of NaOH/CTAB, leading to an improved catalyst lifetime. Co-feeding experiments with short olefins and water show low reactivity of primary MTO products, which only react at the surface of the catalyst particles. These results demonstrate that migration of the reaction zone in case of DDR catalysts hardly affects catalyst stability, product composition and nature of deactivating species. The nature of these species depends mostly on reaction temperature: at low temperatures deactivation occurs mainly due to the formation of inert adamantane species, while at high temperatures poly-condensed aromatic hydrocarbons play the major role in deactivation.

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Three supramolecular isomers of lutetium metal-organic framework, {Lu2(H2O)4(ATA)3·4H2O}n (Lu-ATA@RT), {Lu2(H2O)2(C3H7NO)2(ATA)3}n (Lu-ATA@100), and {Lu2(C3H7NO)(ATA)3}n (Lu-ATA@150), have been obtained from the reaction of Lu(NO3)3·6H2O with 2-aminoterephthalic acid (ATA) at different temperatures. The resulting structures of Lu-ATA metal-organic frameworks depend on the temperature applied during the synthesis, revealing a temperature-susceptible supramolecular isomerism. Single-crystal X-ray diffraction analyses suggest that new compounds with formula {Lu2(S)x(ATA)3}n (S = solvent: H2O, DMF) display different three-dimensional architectures which consist of dinuclear lutetium building units. The supramolecular isomer Lu-ATA@RT, formed at room temperature, has a pcu-net topology, while its double interpenetrated analogue Lu-ATA@100 assembles at 100 °C under hydrothermal conditions. Hydrothermal synthesis at 150 °C affords formation of the dense Lu-ATA@150 cage-like framework displaying a new hexagonal-packed net topology. All Lu-ATA isomeric phases are porous and display different gas-uptake behavior toward carbon dioxide as a function of polymeric network arrangement. The luminescent properties of Lu-ATA frameworks in the solid state as well as in suspension in the presence of different solvents reveal a solvent-dependent emission.@en

Mixed-matrix membranes (MMMs) comprising Matrimid and a microporous azine-linked covalent organic frameworks (ACOF-1) were prepared and tested in the separation of CO₂ from an equimolar CO₂/CH₄ mixture. The COF-based MMMs show a more than doubling of the CO₂ permeability upon 16 wt % ACOF-1 loading together with a slight increase in selectivity compared to the bare polymer. These results show the potential of COFs in the preparation of MMMs.

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C14H16N2O6, triclinic, P1 (no. 2), a = 10.0254(5) Å, b = 11.2726(6) Å, c = 13.4494(7) Å, α = 111.535(2)°, β = 92.068(2)°, γ = 102.644(2)°, V = 1368.16(13) Å3, Z = 4, Rgt(F) = 0.047, wRref(F2) = 0.133, T = 150 K.@en