Hollow Microcrystals of Copper Hexafluoroacetylacetonate-Pyridine Derivative Adducts via Supercritical CO2 Recrystallization

An innovative crystallization process, based in the use of the eco-friendly supercritical carbon dioxide (scCO2) solvent, is presented for the production of coordination compounds macrocrystals of general formula [Cu(hfacac)2(dPy)2], with intriguing prismatic hollow structures and single polymorphic forms. On the contrary, conventional solvents yielded compact microstructures. Studied pyridine derivatives (dPy) were 4-phenylpyridine, PhPy; 4-benzylylpyridine, BzPy; and 4-acetylpyridine, AcPy. In the specific case of the [Cu(hfacac)2(AcPy)2] adduct, the use of scCO2 as a solvent allows obtaining a pure polymorph, while the conventional solvent trials yielded a mixture of two polymorphs. Four new crystalline structures have been resolved from single crystal X-ray diffraction. All the structures consist in mononuclear complexes connected through intermolecular interactions, including H···H, H···O, F···F, C-F···Caromatic and/or C-F··· interactions, generating bidimensional networks that determine their crystallization mode in scCO2.This work was partially financed by the Spanish National Plan of Research CTQ2014-56324 and Severo Ochoa SEV-2015-0496, and by the Generalitat de Catalunya 2014SGR377. A. López-Periago acknowledges the RyC-2012-11588 contract. ALBA synchrotron is acknowledged for the provision of beamtime.Peer Reviewe

Exploring a novel preparation method of 1D metal organic frameworks based on supercritical CO2

The preparation of copper(II) one-dimensional MOFs using an eco-efficient method is reported here. This method is based exclusively on using supercritical CO2 as a solvent, without the addition of any other additive or co-solvent. Neutral acetylacetonate copper complexes and two linear linkers, namely, the bidentate 4,4¿-bipyridine and 4,4¿-trimethylenedipyridine molecules, were reacted under compressed CO2 at 60 °C and 20 MPa for periods of 4 or 24 h. The success achieved in the synthesis of the different studied 1D-MOFs was related to the solubility of the reagents in supercritical CO2. The reaction yield of the synthesized coordination polymers via the supercritical route was close to 100% because both the reactants were almost completely depleted in the performed experiments. © The Royal Society of Chemistry 2015.This work was partially financed by EU COST project MP1202 OC-2011-2-10820 and by the Generalitat de Catalunya 2014SGR377. A. López-Periago acknowledges the RyC-2012- 11588 contract. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer Reviewe

Spectroscopic analysis of triflusal impregnated into PMMA from supercritical CO2 solution

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[Zn2Ac2(μ-Ac)2(bpymb)]n (Ac, acetate; bpymb, 1,4-bis(4-pyridylmethyl)benzene), a 2D coordination polymer obtained with a flexible N,N’-ditopic bipyridine linker

The combination of the flexible N,N’-ditopic ligand 1,4-bis(4-pyridylmethyl)benzene (bpymb) with zinc(II) acetate (ZnAc) affords the synthesis of the two-dimensional coordination polymer [Zn2Ac2(μ-Ac)2(bpymb)]n, which was structurally characterized by single crystal XRD. In the resolved structure, the molar ratio metal:ligand was 2:1 for Ac:Zn. However, half of the acetate units are acting as bridging ligands, which allows the building of a layered structure. The description of this new structure increases the numerous family of compounds involving zinc acetate and a ditopic N,N’- ligand, and demonstrates a new possible architecture. The obtained coordination polymer was also characterized by elemental analysis, ATR-FTIR spectroscopy and TGA analysis. Besides, the photoluminescence properties of this compound where measured, showing that the weak photoluminescence of the free bpymb ligand increases after polymer formation.This work was financed by the Spanish National Plan of Research with project CTQ2017-83632. C.D. and A.M.L.-P. acknowledge the financial support from the Spanish MEC, through the Severo Ochoa Program for Centres of Excellence in R&D FUNFUTURE (CEX2019-000917-S). ALBA synchrotron is acknowledged for the provision of beam time.Peer reviewe

Porosity and water permeability study of supercritically carbonated cement pastes involving mineral additions

The objective of this ongoing work is to improve the physical properties of Portland cement pastes and Portland-composite cement pastes containing silica fume and/or fly ash through an accelerated carbonation process based on the use of SCCO2. Cement carbonation allows the preparation of cementitious composites reinforced with low-cost alkali-intolerant products and the use of these materials in solidification/stabilization of hazardous waste. In the supercritical treatment, results suggested that the carbonation rate of the portlandite phase slowed down after the first reaction stage and was overtaken by the reaction rate of the CSH and ettringite phases. Samples carbonated under the supercritical conditions developed a higher volume of gel pores than those obtained by natural carbonation. The microstructural analysis was completed by analyzing the water permeability of a cement paste/sand composite (mortar) after supercritical carbonation. Obtained values showed that supercritical carbonation reduced water permeability significantl

One-dimensional metal–organic frameworks built by coordinating 2,4,6-tris(4-pyridyl)-1,3,5-triazine linker with copper nodes: CO2 adsorption properties

The reaction between 2,4,6-tris(4-pyridyl)-1,3,5-triazine (4-tpt) and copper(II) hexafluoroacetylacetone (Cu(hfa)2) yields two different 1D metal–organic frameworks (MOFs), [(Cu(hfa)2)2(4-tpt)]n (1) and [Cu(hfa)2(4-tpt)]n (2). The Cu:4-tpt ratio in the new MOFs is determined by the reaction medium, particularly, the solvent used. The two compounds have been fully characterized, including crystal structure elucidation. [(Cu(hfa)2)2(4-tpt)]n (1), with a 2:1 Cu:4-tpt ratio, could be precipitated in either 1,1,2-trichloroethane or supercritical CO2. In (1), 4-tpt shows a tritopic coordination mode, but only half of the Cu(hfa)2 subunits act as a node, thus connecting two 4-tpt and giving a 1D network. The other half of Cu(hfa)2 subunits are connected only to one pyridine and thus protrude along the chains. The later Cu(hfa)2 fragments show a labile character and can be dissolved in diethyl ether to give the second MOF [Cu(hfa)2(4-tpt)]n (2), with a 1:1 Cu:4-tpt ratio. The compound (2) has also a 1D structure, with all the incorporated copper atoms acting as nodes. In this case, the packing of the chains defines accessible channels, which are perpendicular to the chain axis. After activation, N2 adsorption/desorption measurements at 77 K confirm the microporous character of (2) with an apparent surface area of 190 m2 g−1. Besides, at 273 K this material clearly shows a significant adsorption of CO2 prompted by noncoordinated nitrogen in the triazine linker.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) through the Severo Ochoa Program for Centers of Excellence (CEX2019-000917-S) and the Spanish National Plan of Research with project PID2020-115631GB-I00. The measures for the elucidation of the crystal structures were performed at MSPD and XALOC beamlines at ALBA Synchrotron with the collaboration of ALBA staff.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

New insights on the use of supercritical carbon dioxide for the accelerated carbonation of cement pastes

Publicación versión online: 6 de agosto de 2007This study aims to analyze the effects of supercritical carbon dioxide (SCCO2) on the carbonation of Portland cement pastes, with and without mineral addition. The process is based on the advantages of the low viscosity and surface tension of SCCO2 that allow the complete wetting of complex substrates with intricate geometries, including internal surfaces of agglomerates such of these found in cement pastes. The supercritical treatment alters the bulk chemical and structural properties of cement pastes by accelerating natural carbonation reactions, while at the same time it reduces both free and bound water. The observed overall effects of supercritical carbonation on Portland cement pastes were the neutralization of pore water alkalinity, the formation of calcium carbonate and the reduction in the Ca/Si ratio of the calcium silicate hydrate (CSH) gel. Moreover, the massive precipitation of calcium carbonate inside microcracks after supercritical treatment caused the refinement of the microstructure, thus, reducing water permeability to a large extent. Supercritical carbonation method can be completed in few hours, rendering it technically interesting. This work also contributes to the idea of increasing the durability of concrete by means of a preventive hydrophobic supercritical treatment against water ingress. A generic SCCO2 method for concrete silanization is proposed here.The financial support of EU Project STRP SurfaceT NMP2-CT-2005-013524 is greatly acknowledged. Carlos A. García-González gives acknowledgement to CSIC for its funding support through a I3P fellowship.Peer reviewe

Crystalline Curcumin bioMOF obtained by precipitation in supercritical CO2and structural determination by Electron Diffraction Tomography

8sinoneThis article analyzes the use of supercritical CO2green technology in the reactive crystallization processes involved in the formation of a bioMOF that contains curcumin and ZnIImetal centers. A new phase with a [Zn(curcumin)]ncomposition, termed sc-CCMOF-1, is presented. The developed scCO2protocol allows high yields of the small-sized crystalline material, which was characterized by the use of the recently developed electron diffraction tomography method applied to the resolution of submicrometric crystals. A remarkable 3D macrostructure with a complex morphology was obtained. To analyze the crystallization mechanism, multiple identical runs were performed under similar experimental conditions to study in each time period the crystal growth progress ex situ by X-ray diffraction and scanning electron microscopy. These experiments indicated that the process to achieve the sc-CCMOF-1 in a crystalline form involves the formation of amorphous or semicrystalline metastable phases that derived into hierarchical stable and crystalline nanoflower aggregates. In addition, a potential therapeutic application of the bioMOF has been tested by studying the released of the curcumin molecule at neutral pH.nonePortolés-Gil, Nuria; Lanza, Arianna; Aliaga-Alcalde, Núria; Ayllón, José A.; Gemmi, Mauro; Mugnaioli, Enrico*; López-Periago, Ana M.; Domingo, ConcepciónPortolés-Gil, Nuria; Lanza, Arianna; Aliaga-Alcalde, Núria; Ayllón, José A.; Gemmi, Mauro; Mugnaioli, Enrico; López-Periago, Ana M.; Domingo, Concepció

Supramolecular Isomerism in Cobalt(II) Coordination Polymers Built from 3,5-Bis(trifluoromethyl)benzoate and 4,4′-Bipyridine

The reaction of [Co2(H2O)(TFMBz)4(py)4] (1) (TFMBz: 3,5-bis(trifluoromethyl)benzoate; py: pyridine) with 4,4′-bipyridine (bpy) in different solvents yields four coordination polymers with unlikely structures but with the same stoichiometry. Three of them contain similar ladder chains consisting of binuclear nodes "Co2(TFMBz)4", in which two of the TFMBz ligands show bidentate bridge coordination, double linked to each adjacent node by bpy but packed in different fashions. The different packing affects the compound porosity; thus, [Co2(TFMBz)4(bpy)2]n(2), precipitated using low-polarity solvents such as supercritical CO2(scCO2), n-butyl acetate, or heptane and also in acetonitrile, is microporous, with a surface area of 330 m2g-1, showing the N2adsorption/desorption isotherm at 77 K with a gate-opening effect at low relative pressures (P/P0= 0.05). The isomer [Co2(TFMBz)4(bpy)2]n(3), synthesized in ethoxyethanol, presents a surface area of 230 m2g-1. A third chain packing isomer, [Co2(TFMBz)4(bpy)2]n(4), is obtained in acetone and has only non-interconnected voids. Finally, precursor 1 is combined with bpy in a highly polar solvent such as water to give [Co(TFMBz)2(bpy)]n(5). In this isomer, all the carboxylate units act as bidentate bridging ligands, generating chains that are interlinked by bpy, leading to a 2D network, which after packing yields a non-porous structure. The resolution of structures 2-5 is only possible with the recently developed 3D electron diffraction method based on the collection of diffraction patterns on sub-micron-sized single crystals. The variation of magnetic susceptibility as a function of temperature is also measured. Overall, our work provides insightful information on the complex landscape of metal-organic framework solids that are formed by crystallization using different solvent media.This work was supported by the Spanish Ministry of Science and Innovation MICINN through the Severo Ochoa Program for Centers of Excellence (CEX2019-000917-S) and the Spanish National Plan of Research with projects PID2020-115631GB-I00. F.P., A.E.L., and M.G. would like to thank Regione Toscana for funding the purchase of the ASI MEDIPIX detector through the FELIX project (POR CREO FERS 2014–2020). The measures for the elucidation of the crystal structure of compound 1 were performed at the XALOC beamline at ALBA Synchrotron with the collaboration of ALBA staff.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe