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Abstract: We report two three-dimensional metal-organic frameworks constructed from Fe3+ and the ligand, 2,5-furandicarboxylate (FDC) that can be derived from biomass. One contains an unprecedented infinite-rod-shaped building unit, and the other is the first crystalline framework of FDC that contains solely iron in the metal nodes. The materials are formed as microcrystals and their structures determined using 3D-electron diffraction with the bulk confirmed by powder XRD. UOW-7, NaFe5O3(FDC)4(CH3COO)2 is a bimetallic structure with acetate as co-ligand, constructed from infinite chains of iron octahedra, wherein tetramers comprising edge-sharing pairs linked by corner sharing octahedra are crosslinked by FDC ligands. In contrast, UOW-8, Fe2O(FDC)2(H2O)2]·(H2O)4 contains a rare form of tetrameric building unit, cross-linked by FDC, and having Fe-bound water as well as occluded water. The materials crystallise under hydrothermal conditions and are water-stable coordination polymers with no measurable free pore space. The catalytic ability of UOW-7 and UOW-8 is, nevertheless, established in the reduction of 4-nitrophenol to 4-aminophenol by borohydride, where both act as recyclable, catalysts to give ~100% yield of the product without use of precious metals. UOW-8 is found to have the more favourable reaction kinetics, likely due to the presence of surface Lewis acidic Fe3+ centres that enhance substrate binding.

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Abstract: The electron beam for scanning transmission electron microscopy (STEM) provides rich information about the atomic structure and chemical composition of materials from micron to atomic scale. However, the electron probe can also damage the materials of interest, as the high-energy electrons are often focused on very small sample regions. These effects limit the quality of information which can be extracted from experiments on beam-sensitive materials, such as Li-ion battery materials and metal halide perovskites used in solar cell devices. However, with the increasing interest in these materials to address environmental and societal concerns, a detailed understanding of their microstructure and chemical composition at high spatial resolution is needed to improve their performance and stability. For these materials, the correlation between processing and nanoscale structure-property relationships has been difficult to firmly establish. As shown in Fig. 1a-1c, phase change or amorphisation in beam-sensitive materials can be easily caused by a focused electron probe. Fortunately, this problem can be solved through combined scanning electron nano-diffraction (SEND) and energy dispersive X-ray spectroscopy (EDX) with low electron dose conditions, providing nanoscale crystallographic and chemical information from the specimen. However, the signal-to-noise (SNR) of the EDX data is very poor - with just a few counts in any individual scan prohibiting comprehensive materials characterisation (Fig. 1d). To address this, we perform automated SEND-EDX data acquisition under low dose conditions utilising our automated data analysis workflow. By communicating with two different modalities, i.e., Aztec®; Oxford Instruments and MerlinEM; Quantum Detectors, and using our Python-based software, many SEND-EDX data pairs were simultaneously acquired from a metal halide perovskite. The radially flattened diffraction datasets were then be segmented into distinct phases by using an unsupervised learning approach, non-negative matrix factorisation, and the EDX spectra from identical phases classified earlier were summed across all datasets to enable chemical identification with a much higher SNR than one EDX spectrum image (Fig. 1d) as shown in Fig. 2. In this way we can determine the chemical and crystallographic structure of small phase domains in a highly beam-sensitive multi-phase metal halide perovskite. This research will both demonstrate a novel multi-modal, data-fusion based approach to imaging beam-sensitive materials and shed light on the processing and structure-property relationships of these materials on the nanometre length scale to improve their long-term operational stability.

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Abstract: Triboelectric nanogenerator (TENG) based on the coupling effect of triboelectrification and electrostatic induction can convert mechanical motions into electric energy. Recent studies have found that metal–organic framework materials are promising triboelectric materials due to their large surface area and excellent tunability. In this study, we incorporated isostructural zeolitic imidazolate frameworks, ZIF-8-X (X = CH3, Br, Cl), into poly(vinylidene fluoride) (PVDF) electrospun fibers and assembled them in TENG devices to investigate the underlying relationship between functional group electronegativity (via varied imidazolate linkers) and triboelectric output performance. Results show that ZIF-8-Cl/PVDF composite fiber demonstrated the highest average voltage and current output of 312.4 ± 2.0 V and 4.90 ± 0.07 μA, respectively, which are 3.8 and 5.5 times higher than that of the pristine PVDF. The practicality of ZIF-8-X-based TENG was tested for harvesting energy from oscillatory motions to power up LEDs and capacitors. A freestanding mode TENG based on ZIF-8-Cl was also designed to harvest rotational energy without physical contact for wider applications. The working mechanism of ZIF-8-X-based TENG was also revealed through nanoscale-resolved chemical studies, providing valuable insights into the design of MOF materials for improved performance of TENGs.

Open Access

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Abstract: Magnesium (Mg)-based implants have become an attractive alternative to conventional permanent implants in the orthopedic field. While biocompatibility, degradation kinetics, and osseointegration of Mg-based implants have been mostly investigated, the impact of degradation products on bone remodeling and potential systemic effects remains unclear. The aim of this study was to evaluate the early and mid-term local and systemic tissue responses of degrading ultrahigh-purity ZX00 (Mg–Zn–Ca alloy) and ultrahigh-purity Mg (XHP-Mg) pins in a juvenile healthy rat model. The potential differences between implant types (degradable vs. permanent), implantation, and age-related changes were investigated using titanium (Ti), sham-operated, and control groups (non-intervention), respectively. Degradation products of ZX00 and XHP-Mg pins promote osteogenesis in the medullary cavity by upregulating the expression levels of Bmp2 and Opg within 14 days post-surgery. The higher degradation rate of XHP-Mg resulted in the accumulation of degradation products starting from day 3 and upregulation of different genes, particularly Ccl2 and Cepbp. Besides good osseointegration and new bone tissue formation, we found a more parallel hydroxyapatite/collagen orientation along Mg-based pins in the perimeter region compared to Ti pins. In the liver, reduced glycogen levels in Mg-based pins indicated that degradation products promote glycogenolysis, while only the ZX00 group showed a higher serum glucagon level on day 14. Results suggest that degrading ZX00 and XHP-Mg pins stimulate osteogenesis mainly via Bmp2 and Opg and promote glycogenolysis in the liver, while the higher degradation rate of XHP-Mg pins resulted in upregulation of different genes and metabolites.

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Abstract: Integrating metal–organic frameworks (MOFs) into microfabrication processes will benefit from controlled vapor-phase deposition techniques. This study presents a molecular layer deposition method that enables area-selective and oriented growth of zeolitic imidazolate framework-8 (ZIF-8) films. Substrates functionalized with self-assembled monolayers (SAMs) with different end groups (alkyl, phenyl, hydroxyl, carboxyl, amine, and imidazole) allow tuning the degree of crystallographic orientation in the resulting MOF layers. Spatial control over SAM formation determined the surface mobility of the ZIF-8 building blocks, which enabled area-selective deposition.