Structure of the calcium pyrophosphate monohydrate phase (Ca2P2O7·H2O): towards understanding the dehydration process in calcium pyrophosphate hydrates

Calcium pyrophosphate hydrate (CPP, Ca2P2O7·nH2O) and calcium orthophosphate compounds (including apatite, octa­calcium phosphate etc.) are among the most prevalent pathological calcifications in joints. Even though only two dihydrated forms of CPP (CPPD) have been detected in vivo (monoclinic and triclinic CPPD), investigations of other hydrated forms such as tetra­hydrated or amorphous CPP are relevant to a further understanding of the physicochemistry of those phases of biological inter­est. The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM; Ca2P2O7·H2O) by diffusion in silica gel at ambient temperature and the structural analysis of this phase are reported in this paper. Complementarily, data from synchrotron X-ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetra­hydrated calcium pyrophosphate [beta] phase (CPPT-[beta]) is discussed

A Novel Porous Ti-Squarate as Efficient Photocatalyst in the Overall Water Splitting Reaction under Simulated Sunlight Irradiation

A new porous titanium(IV) squarate metal–organic framework (MOF), denoted as IEF-11, having a never reported titanium secondary building unit, is successfully synthesized and fully characterized. IEF-11 not only exhibits a permanent porosity but also an outstanding chemical stability. Further, as a consequence of combining the photoactive Ti(IV) and the electroactive squarate, IEF-11 presents relevant optoelectronic properties, applied here to the photocatalytic overall water splitting reaction. Remarkably, IEF-11 as a photocatalyst is able to produce record H amounts for MOF-based materials under simulated sunlight (up to 672 µmol g in 22 h) without any activity loss during at least 10 d.P.S.-A. and A.A.B. contributed equally to this work. The authors acknowledge the Ramón Areces Foundation project H+MOFs, the M-ERA-NET C-MOF-cell (grant PCI2020-111998 funded by MCIN/AEI /10.13039/501100011033 and European Union NextGenerationEU/PRTR) project, and Retos Investigación MOFSEIDON (grant PID2019-104228RB-I00 funded by MCIN/AEI/10.13039/501100011033) project. S.N. thanks financial support by Ministerio de Ciencia, Innovatión y Universidades RTI2018-099482-A-I00 project and Agència Valenciana de la Innovació (AVI, INNEST/2020/111) project. H.G. thanks financial support to the Spanish Ministry of Science and Innovation (Severo Ochoa and RTI2018-098237-CO21) and Generalitat Valenciana (Prometeo2017/083). T.W. acknowledges financial support from the Swedish Research Council (VR, 2019-05465). Parts of this research were carried out at “CRISTAL” at SOLEIL. P.S. and A.A.B. sincerely thank to the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020 for the support of the synchrotron experiment

A highly conductive nanostructured PEDOT polymer confined into the mesoporous MIL-100(Fe)

[EN] Despite the higher efficiency, larger color range and faster stimulus response of polymeric electrochromic materials, their poor cyclability strongly hampers their application in optoelectronics. As an original strategy to stabilize and further nanostructure these polymers, herein an efficient encapsulation and in situ polymerization inside highly porous metal-organic frameworks (MOFs) is reported. In particular, the successful accommodation of poly(3,4-ethylendioxythiophene) (PEDOT) and its partially oxidized polarons inside the mesopores of the nontoxic iron trimesate MIL-100(Fe) is convincingly proved by a large panel of experimental techniques. Remarkably, the polymer-MOF interaction occurring for entrapped PEDOT within the pores (deeply assessed by experimental and simulation methods) might be responsible for the enhanced electrical conductivity of the resulting PEDOT@MIL-100(Fe) composite when compared to the insulating MIL-100(Fe) and the conductive free PEDOT. Furthermore, it was possible to observe the electrochromic properties of the PEDOT@MIL-100(Fe) composite, achieving an improved stability and good cyclability as a consequence of the effective protection by the MOF matrix.This work was supported by a 2017 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation (IN[17]_CBB_QUI_0197). The work was also partially supported by IMDEA Energy and Raphuel project (ENE2016-79608-C2-1-R, MINECOAEI/FEDER, UE). PH acknowledges the Spanish Ramon y Cajal Programme (grant agreement no. 2014-16823). S. N. thanks the Spanish Ministerio de Educacion, Cultura y Deporte for Jose Castillejo mobility programme (CAS14/00067) and financial support by Fundacion Ramon Areces (XVIII Concurso Nacional para la Adjudicacion de Ayudas a la Investigacion en Ciencias de la Vida y de la Materia, 2016). We also thank the synchrotron Soleil for providing access to the Cristal beamline.Salcedo-Abraira, P.; Santiago-Portillo, A.; Atienzar Corvillo, PE.; Bordet, P.; Salles, F.; Guillou, N.; Elkaim, E.... (2019). A highly conductive nanostructured PEDOT polymer confined into the mesoporous MIL-100(Fe). Dalton Transactions. 48(26):9807-9817. https://doi.org/10.1039/c9dt00917eS980798174826P. M. S. Monk , R. J.Mortimer and D. R.Rosseinsky , Electrochromism: fundamentals and applications , VCH , 1995Kondalkar, V. V., Kharade, R. R., Mali, S. S., Mane, R. M., Patil, P. B., Patil, P. S., … Bhosale, P. N. (2014). Nanobrick-like WO3 thin films: Hydrothermal synthesis and electrochromic application. Superlattices and Microstructures, 73, 290-295. doi:10.1016/j.spmi.2014.05.039Patil, C. E., Tarwal, N. L., Jadhav, P. R., Shinde, P. S., Deshmukh, H. P., Karanjkar, M. M., … Patil, P. S. (2014). Electrochromic performance of the mixed V2O5–WO3 thin films synthesized by pulsed spray pyrolysis technique. 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Evidence of multiple sorption modes in layered double hydroxides using Mo as structural probe

Layered double hydroxides (LDHs) have been considered as effective phases for the remediation of aquatic environments, to remove anionic contaminants mainly through anion exchange mechanisms. Here, a combination of batch isotherm experiments and X-ray techniques was used to examine molybdate (MoO ) sorption mechanisms on CaAl LDHs with increasing loadings of molybdate. Advanced modeling of aqueous data shows that the sorption isotherm can be interpreted by three retention mechanisms, including two types of edge sites complexes, interlayer anion exchange, and CaMoO precipitation. Meanwhile, Mo geometry evolves from tetrahedral to octahedral on the edge, and back to tetrahedral coordination at higher Mo loadings, indicated by Mo K-edge X-ray absorption spectra. Moreover, an anion exchange process on both CaAl LDHs was followed by in situ time-resolved synchrotron-based X-ray diffraction, remarkably agreeing with the sorption isotherm. This detailed molecular view shows that different uptake mechanisms - edge sorption, interfacial dissolution-reprecipitation - are at play and control anion uptake under environmentally relevant conditions, which is contrast to the classical view of anion exchange as the primary retention mechanism. This work puts all these mechanisms in perspective, offering a new insight into the complex interplay of anion uptake mechanisms by LDH phases, by using changes in Mo geometry as powerful molecular-scale probe.This work has been supported by a grant from Labex OSUG@2020 (Investissements d’avenir - ANR10 LABX56). B.M., A.F.-M., L.C., S.G. and F.C. thank the NEEDS program from the CNRS for funding support. B.M. also thanks the financial support from the China Scholarship Council (CSC)

Advances in the synthesis and structure of α-canaphite: a multitool and multiscale study

α-Canaphite (CaNa2P2O7·4H2O) is a layered calcium disodium pyrophosphate tetrahydrate phase of significant geological and potential biological interest. This study overcomes the lack of a reliable protocol to synthesize pure α-canaphite by using a novel simple and reproducible approach of double decomposition in solution at room temperature. The pure α-canaphite is then characterized from the atomic to the macroscopic level using a multitool and multiscale advanced characterization strategy, providing for the first time full resolution of the α-canaphite monoclinic structure, including the hydrogen bonding network. Synchrotron X-ray diffraction and neutron diffraction are combined with multinuclear solid state NMR experimental data and computational modeling via DFT/GIPAW calculations. Among the main characteristics of the α-canaphite structure are some strong hydrogen bonds and one of the four water molecules showing a different coordination scheme. This peculiar water molecule could be the last to leave the collapsed structure on heating, leading eventually to anhydrous α-CaNa2P2O7 and could also be involved in the internal hydrolysis of pyrophosphate ions as it is the closest water molecule to the pyrophosphate ions. Relating such detailed structural data on α-canaphite to its physico-chemical properties is of major interest considering the possible roles of canaphite for biomedical applications. The vibrational spectra of α-canaphite (deuterated or not) are analyzed and Raman spectroscopy appears to be a promising tool for the identification/diagnosis of such microcrystals in vitro, in vivo or ex vivo

An in situ study using Awaxs and Xas of the catalytic system ZnAl2O4 supported on alumina

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Crystal structure of tooeleite, Fe6(AsO3)4SO4(OH)4·4H2O, a new iron arsenite oxyhydroxysulfate mineral relevant to acid mine drainage

International audienceresolution synchrotron XRD powder data recorded on a sample from Tooele county, Utah. The structure is monoclinic, space group C2/m, a = 8.9575(1), b = 6.4238(1), c = 9.7912(1) Å, β = 96.032(1)°, V = 560.27(3) Å3, dcalc = 3.16 g/cm3. The structure was solved by direct methods and atomic positions, site occupancies, and isotropic displacement parameters were reÞ ned by the Rietveld method. The AsO3 pyramids bond to FeO6 octahedra by both edge- and corner-linkage, forming layers that intercalate SO4 groups. Assignment of structural H2O and OH groups were done from bond-valence analysis. Tooeleite is the only arsenite-sulfate mineral known and has been recently identiÞ ed as the main constituent of stromatolite-like deposits in the Carnoulès acid mine, Gard, Franc

In pursuit of the rhabdophane crystal structure: from the hydrated monoclinic LnPO4.0.667H2O to the hexagonal LnPO4 (Ln = Nd, Sm, Gd, Eu and Dy)

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