Single-Crystal-to-Single-Crystal Transformations of Metal-Organic-Framework-Supported, Site-Isolated Trigonal-Planar Cu(I) Complexes with Labile Ligands

Transition-metal complexes bearing labile ligands can be difficult to isolate and study in solution because of unwanted dinucleation or ligand substitution reactions. Metal - organic frameworks (MOFs) provide a unique matrix that allows site isolation and stabilization of well-defined transition-metal complexes that may be of importance as moieties for gas adsorption or catalysis. Herein we report the development of an in situ anion metathesis strategy that facilitates the postsynthetic modification of Cu(I) complexes appended to a porous, crystalline MOF. By exchange of coordinated chloride for weakly coordinating anions in the presence of carbon monoxide (CO) or ethylene, a series of labile MOF-appended Cu(I) complexes featuring CO or ethylene ligands are prepared and structurally characterized using X-ray crystallography. These complexes have an uncommon trigonal planar geometry because of the absence of coordinating solvents. The porous host framework allows small and moderately sized molecules to access the isolated Cu(I) sites and displace the "place-holder" CO ligand, mirroring the ligand-exchange processes involved in Cu-centered catalysis.Ricardo A. Peralta, Michael T. Huxley, Jorge Albalad, Christopher J. Sumby, and Christian J. Doona

Structural modulation of the photophysical and electronic properties of pyrene-based 3D metal-organic frameworks derived from s-block metals

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.Christopher N. Coleman, Patrick C. Tapping, Michael T. Huxley, Tak W. Kee, David M. Huang, Christian J. Doonan and Christopher J. Sumb

Post-Synthetic Modification of a Porous Hydrocarbon Cage to Give a Discrete C024 Organometallic Complex**

First published: 21 July 2022A 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.Chriso M. Thomas, Weibin Liang, Dan Preston, Christian J. Doonan, and Nicholas G. Whit

Testing small molecule analogues of acanthocheilonema viteae immunomodulator ES-62 against clinically relevant allergens

ES-62 is a glycoprotein secreted by the filarial nematode Acanthocheilonema viteae that protects against ovalbumin (OVA)-induced airway hyper-responsiveness in mice by virtue of covalently attached anti-inflammatory phosphorylcholine (PC) residues. We have recently generated a library of Small Molecule Analogues (SMAs) of ES-62 based around its active PC moiety as a starting point in novel drug development for asthma, and isolated two compounds - termed 11a and 12b – that mirror ES-62’s protective effects. In the present study we have moved away from OVA, a model allergen, to test the two SMAs against two clinically relevant allergens – house dust mite (HDM) and cockroach allergen (CR) extract. We show that whereas both SMAs offer some protection against development of lung allergic responses to CR, in particular reducing eosinophil infiltration, only SMA 12b is effective in protecting against eosinophil-dependent HDM-induced allergy. These data therefore suggest that helminth molecule-induced protection against model antigens may not necessarily translate to clinically relevant antigens. Nevertheless, in the present study we have managed to demonstrate that it is possible to produce synthetic drug-like molecules based on a parasitic worm product that show therapeutic potential with respect to asthma resulting from known triggers in humans

Unveiling the structural transitions during activation of a CO2 methanation catalyst Ru0/ZrO2 synthesised from a MOF precursor

Available online 5 May 2020Carbon Capture, Utilisation and Storage (CCUS) technologies are utilised to minimise net CO2 emissions and hence mitigate the impact of anthropogenic emissions on the global climate. One example of CO2 utilisation is the production of carbon-neutral methane fuel via catalytic CO2 reduction with H2 (methanation). Thermal activation of a metal impregnated metal-organic framework (MOF), 1 wt%Ru/UiO-66 in the presence of H2 and CO2 provides in situ synthesis of a highly active methanation catalyst: H2 promotes the formation of Ru0 nanoparticles, and CO2 behaves as a mild oxidant to remove framework carbon and promote ZrO2 crystallisation. The nature of the active MOF-derived Ru0/ZrO2 catalyst was studied by PXRD, TEM, and XAS, and the evolution of the parent 1 wt%Ru/UiO-66 during thermal activation monitored in operando by synchrotron PXRD. The Ru impregnated Zr-based MOF collapses on heating in H2 and CO2 to form an amorphous C and Zr containing phase that subsequently crystallises as tetragonal (t-) ZrO2 nanoparticles. These t-ZrO2 nanoparticles undergo a subsequent phase transition to the more stable monoclinic (m-) ZrO2 polymorph. In situ activation of Ru/UiO-66 generates a highly active catalyst for CO2 methanation by transforming the MOF precursor into a (carbonfree) crystalline t-ZrO2 support that stabilises highly dispersed metallic Ru nanoparticles. This insight may guide the rational design of future MOF-derived catalystsRenata Lippi, Anita M. D, Angelo, Chaoen Li, Shaun C. Howard, Ian C. Madsen, Karen Wilson, Adam F. Lee, Christopher J. Sumby, Christian J. Doonan, Jim Patel, Danielle F. Kenned

Insights into the Interaction between Immobilized Biocatalysts and Metal–Organic Frameworks: A Case Study of PCN-333

The immobilization of enzymes in metal−organic frameworks (MOFs) with preserved biofunctionality paves a promising way to solve problems regarding the stability and reusability of enzymes. However, the rational design of MOF-based biocomposites remains a considerable challenge as very little is known about the state of the enzyme, the MOF support, and their host−guest interactions upon immobilization. In this study, we elucidate the detailed host−guest interaction for MOF immobilized enzymes in the biointerface. Two enzymes with different sizes, lipase and insulin, have been immobilized in a mesoporous PCN333(Al) MOF. The dynamic changes of local structures of the MOF host and enzyme guests have been experimentally revealed for the existence of the confinement effect to enzymes and van der Waals interaction in the biointerface between the aluminum oxo-cluster of the PCN-333 and the -NH2 species of enzymes. This kind of host−guest interaction renders the immobilization of enzymes in PCN-333 with high affinity and highly preserved enzymatic bioactivity.Wenjie Yang, Weibin Liang, Luke A. O, Dell, Hamish D. Toop, Natasha Maddigan, Xingmo Zhang, Alena Kochubei, Christian J. Doonan, Yijiao Jiang, and Jun Huan

Carbohydrates@MOFs

MOFs have demonstrated outstanding properties for the protection and controlled release of different bio-entities, from proteins to living cells. Carbohydrates, as pure molecules or as a component of proteins and cells, perform essential biological functions. Thus, an understanding of the role of carbohydrates in the formation of MOF-based bio-composites will facilitate their application to biotechnology and medicine. Here, we investigate the role of carbohydrate molecular weight and chemical functionalization in the formation of carbohydrate@MOF composites. We find that chemical functionalization, such as carboxylation, that leads to an enhancement of metal cation concentration at the surface of the molecule triggers the rapid self-assembly of the MOF material, zeolitic-imidazolate framework 8 (ZIF-8). Furthermore, we determine the encapsulation efficiency and measure the release properties of the carbohydrate under controlled conditions. Our findings show that MOFs can be used to prepare a new class of biocomposites for the delivery of carbohydrate-based therapeutics.Efwita Astria, Martin Thonhofer … Weibin Liang … David M. Huang, Christian J. Doonan, Paolo Falcaro ... et al

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Tuning packing, structural flexibility, and porosity in 2D metal-organic frameworks by metal node choice

Understanding the key features that determine structural flexibility in metal–organic frameworks (MOFs) is key to exploiting their dynamic physical and chemical properties. We have previously reported a 2D MOF material, CuL1, comprising five-coordinate metal nodes that displays exceptional CO₂/N₂ selectively (L1 = bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane). Here we examine the effect of utilising six-coordinate metal centres (Coᶦᶦ and Niᶦᶦ) in the synthesis of isostructural MOFs from L1, namely CoL1 and NiL1. The octahedral geometry of the metal centre within the MOF analogues precludes an ideal eclipse of the 2D layers, resulting in an offset stacking, and in certain cases, the formation of 2-fold interpenetrated analogues β-CoL1 and β-NiL1. We used a combination of thermogravimetric analysis (TGA), and powder and single crystal X-ray diffraction (PXRD and SCXRD) to show that desolvation is accompanied by a structural change for NiL1, and complete removal of the coordinated H₂O ligands results in a reduction in long-range order. The offset nature of the 2D layers in combination with the structural changes impedes the adsorption of meaningful quantities of gases (N₂, CO₂), highlighting the importance of a five-coordinate metal centre in achieving optimal pore accessibility for this family of flexible materials.Witold M. Bloch, Christian J. Doonan and Christopher J. Sumb

Post-synthetic metalation of metal–organic frameworks

Post-synthetic metalation (PSMet) offers expansive scope for a targeted approach to tailoring the properties of MOFs. Numerous methods for carrying-out PSMet chemistry have been reported, however, these can be categorized into three general strategies: (a) addition to coordinating groups; (b) counter-ion exchange in charged frameworks; or, (c) host-guest encapsulation of metal-containing entities within the pores of the framework. PSMet has been applied to enhance the performance characteristics of parent MOFs for gas storage and separation, and catalysis. Notably, PSMet is a prominent strategy in the field of MOF catalysis as it offers a route to design size-selective catalysts, based on the premise of reticular chemistry in MOFs and the ability to incorporate a range of catalytically-active metal centres. Other applications for materials produced via or utilising PSMet strategies include enhancing gas storage or molecular separations, the triggered release of drugs, sensing and tunable light emission for luminescent materials. This review surveys seminal examples of PSMet to highlight the broad scope of this technique for enhancing the performance characteristics of MOFs and to demonstrate how the PSMet concept can be developed for future applications