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The design criteria needed for the formation of the sqc metal–organic framework (MOF) topology, from an 8-connecting node and a 4-connecting linker, are unclear due to a limited number of reports. After recently reporting the MOF UAM-1000 (UAM = University of Adelaide Material), which has this rare sqc topology, we present a study that explores the effect of flexible tetrapyrazole carboxylate linker structure metrics on the topology of Zirconium-based MOFs (Zr-MOFs). By modifying the linker length and width, three new Zr-MOFs (UAM-10, UAM-11, and UAM-1002) were synthesized and characterized. The study reveals that linker dimensions influence the accessible conformations, and along with fine-tuning of synthetic conditions, allow control over MOF topology. Additionally, linker flexibility plays a crucial role in the formation of the sqc over the more common csq topology. Finally, the presence of free bis-pyrazolyl groups in the reported MOFs allowed us to evaluate the potential for post-synthetic metalation (PSMet). UAM-10 and UAM-11 are too rigid, the pyrazole groups lack the appropriate arrangement and therefore these materials do not undergo PSMet. In contrast, UAM-1002 with its scu topology exhibits the right quanta of flexibility needed for successful PSMet, making it a promising platform for studying the chemistry of anchored organometallic complexes. Moreover, the different topology for UAM-1002 versus UAM-1000 changes the nature of the PSMet site (bidentate versus a tetradentate site) despite these being made from the same node and linker building blocks. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) capable of post-synthetic metalation (PSMet) have garnered significant interest as supports for catalytic metals. The Mn-based MOF, MnMOF-1 ([Mn3(L2Me)3] where L2Me = bis-(4-carboxyphenyl-3,5-dimethylpyrazolyl)methane), has been an exemplar for studying PSMet. Herein we investigate the synthesis of Mn-based MOFs from related flexible ditopic pyrazole carboxylate links, along with the formation of MOFs with similar tetratopic hinged linkers. We show for the first time that MnMOF-1 is likely a kinetic or metastable phase and a newly identified 2D layered material (MnMOF-2D) is the thermodynamically favoured product for this metal–linker combination. Formation of a MnMOF-1 structure with shorter linkers is thwarted by steric clashes that preclude the formation of the Mn3 cluster. This observation prompted the use of density functional theory (DFT) simulations that showed the target material to be very dense, highly strained and thereby energetically unfavourable, but potentially, a hypothetical MnMOF-1 structure with a longer phenylethynyl spacer would be energetically feasible. Finally, the predominance of 2D MOFs formed with shorter flexible links encouraged us to use tetratopic hinged linkers to form 3D frameworks, which was vindicated by the successful synthesis of two new porous 3D Mn-based MOFs, MnMOF-L4 and MnMOF-L5. These results highlight that reticular synthesis of MOFs formed with flexible, non-linear linkers is challenging. [ABSTRACT FROM AUTHOR]

In this work, we studied the encapsulation of a range of proteins in a hydrogen-bonded organic framework (HOF) comprised of a tetraamidinium cation and diazobenzene-based dicarboxylate anion. We explore the use of external stimuli: light and temperature to modulate HOF crystal growth and size. In particular, we found photo-isomerisation can be used to control the concentration of the trans-azobenzene building block that contributes to HOF formation. When HOF growth was slowed sufficiently, deformation of the crystals and ultimately multicrystal aggregates were observed in the presence of some proteins. We propose that the extent of crystal deformation, consistent with better protein association, may be governed by differences in the type and strength of interactions between proteins and the surface of the growing HOF crystals. [ABSTRACT FROM AUTHOR]

Anionic hydrogen bonded frameworks were synthesised from di or tetra-amidinium hydrogen bond donor components and a charge "mis-matched" tecton possessing a 5− charge but only four hydrogen bond accepting groups. The net negative charge on the framework skeletons necessitates the presence of a cation in the framework channel. In one of the frameworks, the initially incorporated organic cation was rapidly displaced by smaller inorganic cations, or the cationic dye methylene blue. This facilitated the effective and selective removal of this dye from water. [ABSTRACT FROM AUTHOR]

The article is an editorial from the new co-Editors-in-Chief of CrystEngComm, Christian J. Doonan and C. Malla Reddy. They express their privilege and honor to serve as co-Editors-in-Chief of the journal, which has a reputation for publishing high-quality research on the design and applications of crystalline materials. They acknowledge the outgoing Editor-in-Chief for his excellent stewardship and dedication to maintaining the scientific standards of the journal. The new co-Editors-in-Chief plan to uphold these standards, promote diversity in scientific publishing, and highlight the broad applications of crystal engineering in chemistry. They look forward to leading CrystEngComm into an exciting future. [Extracted from the article]

As hydrogen bonded frameworks are held together by relatively weak interactions, they often form several different frameworks under slightly different synthesis conditions and respond dynamically to stimuli such as heat and vacuum. However, these dynamic restructuring processes are often poorly understood. In this work, three isoreticular hydrogen bonded organic frameworks assembled through charge‐assisted amidinium⋅⋅⋅carboxylate hydrogen bonds (1C/C, 1Si/C and 1Si/Si) are studied. Three distinct phases for 1C/C and four for 1Si/C and 1Si/Si are fully structurally characterized. The transitions between these phases involve extreme yet recoverable molecular‐level framework reorganization. It is demonstrated that these transformations are related to water content and can be controlled by humidity, and that the non‐porous anhydrous phase of 1C/C shows reversible water sorption through single crystal to crystal restructuring. This mechanistic insight opens the way for the future use of the inherent dynamism present in hydrogen bonded frameworks. [ABSTRACT FROM AUTHOR]

Metal–organic framework (MOF) coatings on cells enhance viability in cytotoxic environments. Here, we show how protective multi-layered MOF bio-composite shells on a model cell system (yeast) enhance the proliferation of living cells exposed to hostile protease-rich environments via the dissolution of the shells and release of a protease inhibitor (antitrypsin). [ABSTRACT FROM AUTHOR]

A new alkyne‐based hydrocarbon cage was synthesized in high overall yield using alkyne‐alkyne coupling in the cage forming step. The cage is porous and displays a moderately high BET surface area (546 m2 g−1). The cage loses crystallinity on activation and thus is porous in its amorphous form, while very similar cages have been either non‐porous, or retained crystallinity on activation. Reaction of the cage with Co2(CO)8 results in exhaustive metalation of its 12 alkyne groups to give the Co24(CO)72 adduct of the cage in good yield. [ABSTRACT FROM AUTHOR]

The electronic structures of the cis-MoOS unit is studied by using S K-edge X-ray absorption spectroscopy (XAS) and vibrational spectroscopies coupled with bonding calculations. The electronic structure of the oxidized enzyme site has played a role in polarizing a substrate carbon center for nucleophilic attack by metal activated water and has acted as an electron sink in the two-electron oxidation of substrates.

The structural characterization of Rhodobacter sphaeroides dimethyl sulfoxide (DMSO) reductase reduced with trimethylarsine is presented and shown that it is structurally analogous to the physiologically relevant dimethyl sulfide reduced DMSO reductase. The similarity of the trimethylarsine and dimethyl sulfide complexes has indicated that the dimethyl sulfide reduced enzyme consists of a classical coordination of DMSO with no special elongation of the S-O bond.

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Enzymes incorporated into hydrogen‐bonded organic frameworks (HOFs) via bottom‐up synthesis are promising biocomposites for applications in catalysis and sensing. Here, we explored synthetic incorporation of d‐amino acid oxidase (DAAO) with the metal‐free tetraamidine/tetracarboxylate‐based BioHOF‐1 in water. N‐terminal enzyme fusion with the positively charged module Zbasic2 strongly boosted the loading (2.5‐fold; ≈500 mg enzyme gmaterial−1) and the specific activity (6.5‐fold; 23 U mg−1). The DAAO@BioHOF‐1 composites showed superior activity with respect to every reported carrier for the same enzyme and excellent stability during catalyst recycling. Further, extension to other enzymes, including cytochrome P450 BM3 (used in the production of high‐value oxyfunctionalized compounds), points to the versatility of genetic engineering as a strategy for the preparation of biohybrid systems with unprecedented properties. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of Mo and W complexes with the potential to facilitate progress in Oxo-Mo and -W calixarene chemistry and its applications is presented. The HCI gas evolved from the reaction mixtures by a flow of dinitrogen produced a positive test for chloride when bubbled through silver nitrate solution.

Research was conducted to reexamine the Berg-Holm oxomolybdoenzyme model. The microanalytical, spectroscopic, mass spectrometric and X-ray diffraction data demonstrate that the purple oxo-Mo(IV) complex and its different modifications contain the dinuclear mu-oxo-Mo complex, Mo(super V)2O3(L-NS2)2. The unusual properties of the substance were reconciled by the reformulation of the compound. It also permitted a more complete and accurate description of the Berg-Holm model.

Metal–organic layers (MOLs) are of great interest in heterogeneous catalysis, particularly materials that can accommodate extraneous metal centres. Here, we demonstrate a two-step preorganisation/delamination synthetic strategy using CuI as a template to prepare Zr-based MOLs with accessible 'syn' bis-pyrazolyl chelating sites (named UAM-2·ns) that are poised for quantitative post-synthetic metalation with late transition metals. [ABSTRACT FROM AUTHOR]

The effect of concentration, organic co-solvent, and salt modulators on the crystallisation of a hydrogen bonded framework was studied. The framework contains ∼1.4 nm wide channels and contains a diazobenzene based dicarboxylate anion. Light-induced cis/trans switching of this anion was also used to control crystallisation. [ABSTRACT FROM AUTHOR]

Processing oriented metal–organic frameworks (MOFs) as thin films is a key challenge for their application to device fabrication. However, typical fabrication methods cannot generate precisely oriented crystals on commercially relevant scales (i.e., cm2). This limits access to applications that require anisotropic functional properties (e.g., separation, optics, and electronics). Currently, highly oriented copper‐based MOFs are synthesized via the addition of the organic MOF component to an ethanolic solution of manually aligned Cu(OH)2 nanobelt films. In this work, the optimization of a semi‐automatic method for the fabrication of precisely oriented MOF films that affords a 100% yield of high quality ceramic films at the centimeter scale is reported. This improved fabrication protocol will facilitate the progress of heteroepitaxially grown MOFs for molecular separators and micro‐opto‐electronic devices. [ABSTRACT FROM AUTHOR]

Three-dimensional electron diffraction (3DED) has been proven as an effective and accurate method for structure determination of nano-sized crystals. In the past decade, the crystal structures of various new complex metal–organic frameworks (MOFs) have been revealed by 3DED, which has been the key to understand their properties. However, due to the design of transmission electron microscopes (TEMs), one drawback of 3DED experiments is the limited tilt range of goniometers, which often leads to incomplete 3DED data, particularly when the crystal symmetry is low. This drawback can be overcome by high throughput data collection using continuous rotation electron diffraction (cRED), where data from a large number of crystals can be collected and merged. Here, we investigate the effects of improving completeness on structural analysis of MOFs. We use ZIF-EC1, a zeolitic imidazolate framework (ZIF), as an example. ZIF-EC1 crystallizes in a monoclinic system with a plate-like morphology. cRED data of ZIF-EC1 with different completeness and resolution were analyzed. The data completeness increased to 92.0% by merging ten datasets. Although the structures could be solved from individual datasets with a completeness as low as 44.5% and refined to a high precision (better than 0.04 Å), we demonstrate that a high data completeness could improve the structural model, especially on the electrostatic potential map. We further discuss the strategy adopted during data merging. We also show that ZIF-EC1 doped with cobalt can act as an efficient electrocatalyst for oxygen reduction reactions. [ABSTRACT FROM AUTHOR]

A study characterized the Kbeta(sub 4) and Kbeta(super '') valence-to-core transition bands in several different oxo-molybdenum compounds by using high-resolution molybdenum K-edge X-ray emission spectroscopy. The results show that the Kbeta(sub 4) and Kbeta(super '') were found to be sensitive to the chemical and electronic environment.

Metal‐organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X‐ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high‐throughput approach for structural analysis of MOF nano‐ and sub‐microcrystals by three‐dimensional electron diffraction (3DED). A new zeolitic‐imidazolate framework (ZIF), denoted ZIF‐EC1, was first discovered in a trace amount during the study of a known ZIF‐CO3‐1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF‐EC1 has a dense 3D framework structure, which is built by linking mono‐ and bi‐nuclear Zn clusters and 2‐methylimidazolates (mIm−). With a composition of Zn3(mIm)5(OH), ZIF‐EC1 exhibits high N and Zn densities. We show that the N‐doped carbon material derived from ZIF‐EC1 is a promising electrocatalyst for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have made inroads in diverse chemical sectors due to the essentially limitless combination of building units and the ability to post-synthetically modify their pore chemistry at the molecular level. The crystalline nature of MOFs permits the use of single crystal X-ray diffraction (SCXRD) to obtain crystallographic snapshots of these transformations, providing invaluable information into the unorthodox chemistry that MOFs can potentially offer. This highlight article aims to provide the reader with the most recent milestones in the use of SCXRD as a vanguard technique to connect molecular-level pore engineering of MOFs with new application fields hitherto unexplored. [ABSTRACT FROM AUTHOR]

Materials in which charge delocalization and migration can be tuned are critical for electronic applications. Crystalline framework materials containing π-rich polycyclic aromatic moieties, such as pyrene, can provide a pathway for fast anisotropic charge transport. The extent of interchromophore interaction for structurally distinct assemblies of the π-conjugated aromatic ligand 4,4′,4′′,4′′′-(1,3,6,8-pyrenetetrayl) tetrabenzoic acid (H4TBAPy) was studied within two novel metal–organic frameworks (MOFs), Na(TBAPy)(DMF) and K(TBAPy)(DMF), via steady-state and time-resolved spectroscopic techniques. Single-crystal X-ray diffraction was used to determine the structures of K(TBAPy)(DMF) and Na(TBAPy)(DMF), which both form 3D MOFs comprising 1D rod-like SBUs surrounded by columnar stacks of TBAPy that are aligned in an eclipsed and x-shaped (staggered) geometry, respectively. Spectroscopic and computational results indicate significant chromophore interactions and potentially fast charge transport. Furthermore, distinct transient emission decay profiles are observed and are attributed to significant differences in the stacking orientation of the organic ligands in the two MOFs. Lastly, the study identifies design principles that may be exploited in the rational construction of s-block based MOFs for microelectronic and sensing applications. [ABSTRACT FROM AUTHOR]

Many framework materials such as metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) are synthesized as polycrystalline powders, which are too small for structure determination by single crystal X-ray diffraction (SCXRD). Here, we show that a three-dimensional (3D) electron diffraction method, namely continuous rotation electron diffraction (cRED), can be used for ab initio structure determination of such materials. As an example, we present the complete structural analysis of a biocomposite, denoted BSA@ZIF-CO3-1, in which Bovine Serum Albumin (BSA) was encapsulated in a zeolitic imidazolate framework (ZIF). Low electron dose was combined with ultrafast cRED data collection to minimize electron beam damage to the sample. We demonstrate that the atomic structure obtained by cRED is as reliable and accurate as that obtained by single crystal X-ray diffraction. The high accuracy and fast data collection open new opportunities for investigation of cooperative phenomena in framework structures at the atomic level. [ABSTRACT FROM AUTHOR]

Obtaining structural information for highly reactive metal-based species can provide valuable insight into important chemical transformations or catalytic processes. Trapping these metal-based species within the cavities of porous crystalline hosts, such as metal–organic frameworks (MOFs), can stabilise them, allowing detailed structural elucidation by single crystal X-ray diffraction. Previously, we have used a bespoke flexible MOF, [Mn3L2L′] (MnMOF-1, where L = bis-(4-carboxyphenyl-3,5-dimethylpyrazolyl)methane and L = L′, but L′ has a vacant N,N′-chelation site), which has a chelating site capable of post-synthetically binding metal ions, to study organometallic transformations and fundamental isomerisation processes. This manuscript will report the underlying conformational flexibility of the framework, demonstrate the solvent dependency of post-synthetic metalation, and show that the structural flexibility of the linker site and framework are critical to controlling and achieving high levels of metal loading (and therefore site occupancy) during chemical transformations. From these results, a set of design principles for linker-based "matrix isolation" and structure determination in MOFs are derived. [ABSTRACT FROM AUTHOR]

The mutable structures of metal–organic frameworks (MOFs) allow their use as novel supports for transition metal catalysts. Herein we prepare an iridium bis(ethylene) catalyst bound to the neutral N-donors of a MOF structure and show that the compound is a stable gas phase ethylene hydrogenation catalyst. The data illustrate the need to carefully consider the inner sphere (support) and outer sphere (anion) chemistry. [ABSTRACT FROM AUTHOR]

Manganese-based metal–organic frameworks (MOFs) metalated with Rh were used as pre-catalysts for CO2 hydrogenation. Activated in situ (80 % H2, 20 % CO2, 350°C), the resulting templated catalysts displayed CO2 conversion of up to 20 %, with CH4 as the main product. Used catalysts were compared with samples templated in 5 % H2/Ar at 350°C using powder X-ray diffraction, electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. It was found that under reducing atmosphere Rh0 nanoparticles formed and organic MOF components decomposed, which allowed growth of MnO or MnCO3 and the formation of a mesh of catalytic Rh0 nanoparticles. Manganese-based MOFs metalated with Rh were used as pre-catalysts for CO2 hydrogenation. The comparison of the MOF-derived catalyst with controls provide insights into the MOF-derivation process. [ABSTRACT FROM AUTHOR]

Luminescent metal–organic frameworks (MOFs) are known to spontaneously self-assemble on human fingerprints. Here, we investigate the different chemical components of fingerprints and determine that MOF growth is predominantly induced by insoluble fatty acids. This finding shows that these simple biomolecules can be employed for the precise positioning of luminescent MOFs. [ABSTRACT FROM AUTHOR]