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Abstract: Advances in the production of two-dimensional (2D) materials such as graphene and MoS2 during the past two decades have spurred the search for other van der Waals materials with distinct functional properties. However, reducing the dimensionality of bulk van der Waals materials can lead to structural rearrangement and chemical degradation, especially in the presence of air. These challenges have slowed the progress of the discovery and analysis of chemically diverse 2D materials. Here, we provide a case study on the shear exfoliation of a class of wide band gap van der Waals materials termed II–VI layered hybrids (II–VI LHs) and show how reducing their dimension influences their structural and chemical stabilities. ZnSe(butylamine) and ZnSe(octylamine) are exfoliated, yielding shear-thinned material whose resistance toward degradation via oxidation is studied in depth by a variety of macro- and microscopic characterization techniques. Mechanical energy input, solvent–ligand interaction, and exposure to ambient conditions all play important roles in the stability of these materials. Our findings suggest that moderately coordinating alkylamine layers stabilize 2D materials that would otherwise degrade during exfoliation and exposure to air.

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Abstract: We report on the development and verification of an enhanced computational model capable of robust predictions and yielding a single descriptor to the successful embedding of guest nanoclusters into the pores of functionalised metal–organic frameworks. Using the predictions of this model, we have been able to embed Pd nanoclusters in the pores of Br-UiO-66 and show that the embedding of Pd nanoclusters in both (OH)2-UiO-66 and (Cl)2-UiO-66 is not successful. Also, using various independent methods, we identified the strong host–guest interactions that anchor the guest nanoclusters inside the Br-UiO-66 framework which result in the surface modification of said nanoclusters. We demonstrated that the level of this surface modification is a direct function of the framework functional groups. This new approach for the rational design of nanocluster–metal–organic framework systems, and a demonstrated tool box for their characterisation, will promote the exploitation of surface modification of nanoclusters via their embedding into functionalised metal–organic framework pores.

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Abstract: Zeolite encapsulated metal nanoparticle catalysts hold great promise for several green and sustainable processes, ranging from environmental remediation to renewable energy and biomass conversion. In particular, the microporous zeolite framework keeps the nanoparticles in a firm grip that can control selectivity and prevent sintering at high temperatures. While progress in the synthesis of mesoporous zeolites continues, the encapsulation of metal nanoparticles remains a challenge that often requires complex procedures and expensive additives. Here, we report a general method to encapsulate both base and noble metal nanoparticles inside the internal voids of a compartmentalized mesoporous zeolite prepared by carbon templating and steam-assisted recrystallization. This results in a remarkable shell-like morphology that facilitates the formation of small metal nanoparticles upon simple impregnation and reduction. When the materials are applied in catalysis, we for instance demonstrate that zeolite encapsulated Ni nanoparticles are highly active, selective and stable catalysts for CO2 methanation (49% conversion with 93% selectivity at 450°C). A reaction where catalysts often suffer from sintering due to the high reaction temperatures. While the introduction of Ni nanoparticles prior to the steam-assisted recrystallization results in the formation of inactive nickel phyllosilicates, noble metals such as Pt do not suffer from this limitation. Therefore, we also demonstrate the synthesis of an active catalyst prepared by the formation of Pt nanoparticles prior to the shell synthesis. We tested the zeolite encapsulated Pt nanoparticles for hydrogenation of linear and cyclic alkenes with increased chain length. The catalysts are active for hydrogenation of oct-1-ene (66% conversion) and cyclooctene (79% conversion) but inactive for the large cyclododecane (<1% conversion), which show that this type of catalyst is highly selective in size selective catalysis. All catalysts are characterized by XRD, TEM, XPS and N2 physisorption.

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Abstract: Metal-organic framework crystal-glass composites (MOF-CGCs) are materials in which a crystalline MOF is dispersed within a MOF glass. In this work, we explore the room temperature stabilization of the open-pore form of MIL-53(Al), usually observed at high-temperature, which occurs upon encapsulation within a ZIF-62(Zn) MOF glass matrix. A series of MOF-CGCs containing different loadings of MIL-53(Al) were synthesized and characterized using X-ray diffraction and nuclear magnetic resonance spectroscopy. An upper limit of MIL-53(Al) that can be stabilized in the composite was determined for the first time. The nanostructure of the composites was probed using pair distribution function analysis and scanning transmission electron microscopy. Notably, the distribution and integrity of the crystalline compo-nent in a sample series was determined, and these findings related to the MOF-CGC gas adsorption capacity in order to identify the optimal loading necessary for maximum CO2 sorption capacity.

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Abstract: It is shown that tilt grain boundaries (GBs) in bilayer 2D crystals of the transition metal dichalcogenide WS2 can be atomically sharp, where top and bottom layer GBs are located within sub‐nanometer distances of each other. This expands the current knowledge of GBs in 2D bilayer crystals, beyond the established large overlapping GB types typically formed in chemical vapor deposition growth, to now include atomically sharp dual bilayer GBs. By using atomic‐resolution annular dark‐field scanning transmission electron microscopy (ADF‐STEM) imaging, different atomic structures in the dual GBs are distinguished considering bilayers with a 3R (AB stacking)/2H (AA′ stacking) interface as well as bilayers with 2H/2H boundaries. An in situ heating holder is used in ADF‐STEM and the GBs are stable to at least 800 °C, with negligible thermally induced reconstructions observed. Normal dislocation cores are seen in one WS2 layer, but the second WS2 layer has different dislocation structures not seen in freestanding monolayers, which have metal‐rich clusters to accommodate the stacking mismatch of the 2H:3R interface. These results reveal the competition between maintaining van der Waals bilayer stacking uniformity and dislocation cores required to stitch tilted bilayer GBs together.