Elucidation of the pre-nucleation phase directing metal-organic framework formation

Metal-organic framework (MOF) crystallization is governed by molecular assembly processes in the pre-nucleation stage. Yet, unravelling these pre-nucleation pathways and rationalizing their impact on crystal formation poses a great challenge since probing molecular-scale assemblies and macroscopic particles simultaneously is very complex. Herein, we present a multimodal, integrated approach to monitor MOF nucleation across multiple length scales by combining in situ optical spectroscopy, mass spectrometry, and molecular simulations. This approach allows tracing initial metal-organic complexes in solution and their assembly into oligomeric nuclei and simultaneously probing particle formation. During Co-ZIF-67 nucleation, a metal-organic pool forms with a variety of complexes caused by ligand exchange and symmetry reduction reactions. We discriminate complexes capable of initiating nucleation from growth species required for oligomerization into frameworks. Co4-nuclei are observed, which grow into particles following autocatalytic kinetics. The geometric and compositional variability of metal-organic pool species clarifies long-debated amorphous zeolitic imidazolate framework (ZIF)-particle nucleation and non-classic pathways of MOF crystallization

The Growth of Metal–Organic Framework Films on Calcium Fluoride and Their Interaction With Reactive Molecules

Spectroscopy on metal–organic framework (MOF) films and the molecular phenomena associated to them is mostly limited to grazing incidence methods. To allow for transmission-based characterization and highlight the applicability of MOFs on transparent substrates, UiO-67, UU-1, and ZIF-8 MOFs are synthesized on CaF2 windows. It is revealed that the growth of the UiO-67 MOF follows a Volmer–Weber mechanism using scanning electron microscopy (SEM). This growth is assisted by growing seeds in solution, which anchor on the film and become part of the intergrown film itself. UU-1, a copper-based MOF, is formed after spin coating the Cu-BTC precursors, showing its characteristic fiber-like morphology and resulting inter-fiber macroporosity. ZIF-8 is formed using a “flash”-synthesis, and it is shown that this approach resembles a Volmer–Weber growth mode as well. Last, CO probe molecule adsorption FT-IR spectroscopy is utilized to study the effect of methanol exposure. UiO-67 becomes inaccessible toward CO, due to the formation of methoxy species, whereas UU-1 undergoes a topotactic transformation to HKUST-1. ZIF-8 is the most stable as methanol only removes impurities from the framework. This approach opens the venue for other film materials to be studied in situ synthesis, sorption, or catalysis using transmission-based spectroscopy

Effectiveness of an intervention for improving drug prescription in primary care patients with multimorbidity and polypharmacy:Study protocol of a cluster randomized clinical trial (Multi-PAP project)

This study was funded by the Fondo de Investigaciones Sanitarias ISCIII (Grant Numbers PI15/00276, PI15/00572, PI15/00996), REDISSEC (Project Numbers RD12/0001/0012, RD16/0001/0005), and the European Regional Development Fund ("A way to build Europe").Background: Multimorbidity is associated with negative effects both on people's health and on healthcare systems. A key problem linked to multimorbidity is polypharmacy, which in turn is associated with increased risk of partly preventable adverse effects, including mortality. The Ariadne principles describe a model of care based on a thorough assessment of diseases, treatments (and potential interactions), clinical status, context and preferences of patients with multimorbidity, with the aim of prioritizing and sharing realistic treatment goals that guide an individualized management. The aim of this study is to evaluate the effectiveness of a complex intervention that implements the Ariadne principles in a population of young-old patients with multimorbidity and polypharmacy. The intervention seeks to improve the appropriateness of prescribing in primary care (PC), as measured by the medication appropriateness index (MAI) score at 6 and 12months, as compared with usual care. Methods/Design: Design:pragmatic cluster randomized clinical trial. Unit of randomization: family physician (FP). Unit of analysis: patient. Scope: PC health centres in three autonomous communities: Aragon, Madrid, and Andalusia (Spain). Population: patients aged 65-74years with multimorbidity (≥3 chronic diseases) and polypharmacy (≥5 drugs prescribed in ≥3months). Sample size: n=400 (200 per study arm). Intervention: complex intervention based on the implementation of the Ariadne principles with two components: (1) FP training and (2) FP-patient interview. Outcomes: MAI score, health services use, quality of life (Euroqol 5D-5L), pharmacotherapy and adherence to treatment (Morisky-Green, Haynes-Sackett), and clinical and socio-demographic variables. Statistical analysis: primary outcome is the difference in MAI score between T0 and T1 and corresponding 95% confidence interval. Adjustment for confounding factors will be performed by multilevel analysis. All analyses will be carried out in accordance with the intention-to-treat principle. Discussion: It is essential to provide evidence concerning interventions on PC patients with polypharmacy and multimorbidity, conducted in the context of routine clinical practice, and involving young-old patients with significant potential for preventing negative health outcomes. Trial registration: Clinicaltrials.gov, NCT02866799Publisher PDFPeer reviewe

A database of freshwater fish species of the Amazon Basin

The Amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project - https://www.amazon-fish.com/. Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation

Multi-Spectroscopic Interrogation of the Spatial Linker Distribution in Defect-Engineered Metal–Organic Framework Crystals: The [Cu3(btc)2−x(cydc)x] Showcase

In the past few years, defect-engineered metal–organic frameworks (DEMOFs) have been studied due to the plethora of textural, catalytic, or magnetic properties that can be enhanced by carefully introducing defect sites into the crystal lattices of MOFs. In this work, the spatial distribution of two different non-defective and defective linkers, namely 1,3,5-benzenetricarboxylate (BTC) and 5-cyano-1,3-benzenedicarboxylate (CYDC), respectively, has been studied in different DEMOF crystals of the HKUST-1 topology. Raman micro-spectroscopy revealed a nonhomogeneous distribution of defect sites within the [Cu3(btc)2−x(cydc)x] crystals, with the CYDC linker incorporated into defect-rich or defect-free areas of selected crystals. Additionally, advanced bulk techniques have shed light on the nature of the copper species, which is highly dynamic and directly affects the reactivity of the copper sites, as shown by probe molecule FTIR spectroscopy. Furthermore, electron microscopy revealed the effect of co-crystallizing CYDC and BTC on the crystal size and the formation of mesopores, further corroborated by X-ray scattering analysis. In this way we have demonstrated the necessity of utilizing micro-spectroscopy along with a whole array of bulk spectroscopic techniques to fully describe multicomponent metal–organic frameworks

Influence of Pore Structure and Metal-Node Geometry on the Polymerization of Ethylene over Cr-Based Metal–Organic Frameworks

Metal–organic frameworks (MOFs) have received increasing interest as solid single-site catalysts, owing to their tunable pore architecture and metal node geometry. The ability to exploit these modulators makes them prominent candidates for producing polyethylene (PE) materials with narrow dispersity index (Ð) values. Here a study is presented in which the ethylene polymerization properties, with Et2AlCl as activator, of three renowned Cr-based MOFs, MIL-101(Cr)-NDC (NDC=2,6-dicarboxynapthalene), MIL-53(Cr) and HKUST-1(Cr), are systematically investigated. Ethylene polymerization reactions revealed varying catalytic activities, with MIL-101(Cr)-NDC and MIL-53(Cr) being significantly more active than HKUST-1(Cr). Analysis of the PE products revealed large Ð values, demonstrating that polymerization occurs over a multitude of active Cr centers rather than a singular type of Cr site. Spectroscopic experiments, in the form of powder X-ray diffraction (pXRD), UV/Vis-NIR diffuse reflectance spectroscopy (DRS) and CO probe molecule Fourier transform infrared (FTIR) spectroscopy corroborated these findings, indicating that indeed for each MOF unique active sites are generated, however without alteration of the original oxidation state. Furthermore, the pXRD experiments indicated that one major prerequisite for catalytic activity was the degree of MOF activation by the Et2AlCl co-catalyst, with the more active materials portraying a larger degree of activation

In Situ Spectroscopy of Calcium Fluoride Anchored Metal–Organic Framework Thin Films during Gas Sorption

Surface-mounted metal–organic frameworks (SURMOFs) show promising behavior for a manifold of applications. As MOF thin films are often unsuitable for conventional characterization techniques, understanding their advantageous properties over their bulk counterparts presents a great analytical challenge. In this work, we demonstrate that MOFs can be grown on calcium fluoride (CaF2) windows after proper functionalization. As CaF2 is optically (in the IR and UV/Vis range of the spectrum) transparent, this makes it possible to study SURMOFs using conventional spectroscopic tools typically used during catalysis or gas sorption. Hence, we have measured HKUST-1 during the adsorption of CO and NO. We show that no copper oxide impurities are observed and also confirm that SURMOFs grown by a layer-by-layer (LbL) approach possess Cu+ species in paddlewheel confirmation, but 1.9 times less than in bulk HKUST-1. The developed methodology paves the way for studying the interaction of any adsorbed gases with thin films, not limited to MOFs, low temperatures, or these specific probe molecules, pushing the boundaries of our current understanding of functional porous materials

Ethylene Polymerization over Metal-Organic Framework Crystallites and the Influence of Linkers on Their Fracturing Process

The physical properties and morphologies of polymers are pivotal for their manufacturing and processing at the industrial scale. Here, we present the formation of either fibers or micrometer-sized polyethylene beads by using the MIL-100(Cr) and MIL-101(Cr) zeotypes. The MOF structures have been used for ethylene polymerization with diethylaluminum chloride (DEA) as a cocatalyst, resulting in very different activities and morphologies. In situ DR UV–vis–NIR and CO-probe FT-IR spectroscopy revealed the formation of different types of Cr species for each catalyst material, suggesting that the linker (for the same metal and topological structure) plays a crucial role in the formation of Cr olefin polymerization sites. Activity in ethylene polymerization in toluene at 10 bar and 298 K was related to the observed spectra, corroborating the presence of different types of active sites, by their different activities for high-density polyethylene (HDPE) formation. SEM micrographs revealed that although MIL-100 and MIL-101 exhibit identical zeolitic MTN topology, only the latter is able to collapse upon addition of DEA and subsequent ethylene insertion and to fracture forming polymer beads, thus showing noticeable activity in HDPE formation. We ascribed this effect to the higher pore volume and, thus, fragility of MIL-101, which allowed for polymer formation within its larger cages. MOFs were compared to the nonporous chromium(III) benzoate [Cr3O(O2CPh)6(H2O)2](NO3)·nH2O complex (1), in order to study the effect of the embodiment in the porous framework. The properties of the polymer obtained under identical reaction conditions were comparable to that of MIL-101(Cr) but very different morphologies were observed, indicating that the MIL-101(Cr) structure is necessary to impart a certain architecture at the microscale. This work clearly shows that MOFs can be used as catalytically active morphology regulators for ethylene polymerization. Moreover, even for an identical topology and metal in a MOF structure, the linker and the pore structure play crucial roles and have to be carefully considered in the design microporous coordination polymers for catalytic purposes

Ethylene Polymerization over Metal-Organic Framework Crystallites and the Influence of Linkers on Their Fracturing Process

The physical properties and morphologies of polymers are pivotal for their manufacturing and processing at the industrial scale. Here, we present the formation of either fibers or micrometer-sized polyethylene beads by using the MIL-100(Cr) and MIL-101(Cr) zeotypes. The MOF structures have been used for ethylene polymerization with diethylaluminum chloride (DEA) as a cocatalyst, resulting in very different activities and morphologies. In situ DR UV–vis–NIR and CO-probe FT-IR spectroscopy revealed the formation of different types of Cr species for each catalyst material, suggesting that the linker (for the same metal and topological structure) plays a crucial role in the formation of Cr olefin polymerization sites. Activity in ethylene polymerization in toluene at 10 bar and 298 K was related to the observed spectra, corroborating the presence of different types of active sites, by their different activities for high-density polyethylene (HDPE) formation. SEM micrographs revealed that although MIL-100 and MIL-101 exhibit identical zeolitic MTN topology, only the latter is able to collapse upon addition of DEA and subsequent ethylene insertion and to fracture forming polymer beads, thus showing noticeable activity in HDPE formation. We ascribed this effect to the higher pore volume and, thus, fragility of MIL-101, which allowed for polymer formation within its larger cages. MOFs were compared to the nonporous chromium(III) benzoate [Cr3O(O2CPh)6(H2O)2](NO3)·nH2O complex (1), in order to study the effect of the embodiment in the porous framework. The properties of the polymer obtained under identical reaction conditions were comparable to that of MIL-101(Cr) but very different morphologies were observed, indicating that the MIL-101(Cr) structure is necessary to impart a certain architecture at the microscale. This work clearly shows that MOFs can be used as catalytically active morphology regulators for ethylene polymerization. Moreover, even for an identical topology and metal in a MOF structure, the linker and the pore structure play crucial roles and have to be carefully considered in the design microporous coordination polymers for catalytic purposes

Impact of Niobium in the Metal-Organic Framework-Mediated Synthesis of Co-Based Catalysts for Synthesis Gas Conversion

We report the use of transition metal precursors impregnated into the pores of CPO-27(Co) metal–organic framework (MOF) crystals prior to pyrolysis as a straightforward strategy for tuning the properties of MOF-derived Co-based catalysts. By adding a Nb inorganic salt prior to pyrolysis hierarchical pores are formed in the resulting carbon and the Co accessible surface area is greatly increased leading to a strong enhancement of CO hydrogenation activity