Confined Water in Mesoporous MCM-41 and Nanoporous AlPO4-5: Structure and Dynamics

Floquet, N.; Coulomb, J.P.; Dufau, Nathalie; André, G.; Kahn, R.

doi:10.1007/s10450-005-5912-9

Cited by 31 publications

(20 citation statements)

References 15 publications

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“…In recent years the effect of confinement on properties of "materials" has been investigated including general aspects, [10] but of course also considering liquids [11] and these especially in context with confined water properties. [12][13][14][15] One possible way to investigate confined water molecule assemblies systematically is by trapping them in structurally well defined and differently sized as well as functionalized nanosized capsule cavities. This is possible with soluble spherical porous capsules of the type [{pentagonal unit} 12 {metal linker unit} 30 [16a,b] which are stable in solution under welldefined conditions, while the pores can, as an important aspect, be closed in a stepwise manner.…”

mentioning

confidence: 99%

Gated and Differently Functionalized (New) Porous Capsules Direct Encapsulates' Structures: Higher and Lower Density Water

Mitra

Miró

Tomsa

et al. 2009

Chemistry A European J

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By the deliberate choice of the internal ligands of the porous nanocapsules [{(Mo)Mo(5)}(12){Mo(2)(ligand)}(30)](n-), the respective cavities' shells can be differently sized/functionalized. This allows one to trap the same large number of water molecules, that is, 100 in a capsule cavity with formate ligands having a larger space available, as well as in a cavity containing sulfates and hypophosphites, that is, with less space. Whereas the 100 molecules fill the space completely in the second case in which they are organized in three shells, a four-shell system with underoccupation and broken hydrogen bonds is observed in the other case. This is an unprecedented result in terms of the structurally well defined special forms of "higher and lower density" water molecule assemblies. Precisely, by replacing the larger ligands in the mentioned nanocapsule type by formates, voids in the capsule cavity of (HC(NH(2))(2))(22)[{(HC(NH(2))(2))(20)+(H(2)O)(100)} subset{(Mo)Mo(5)O(21)(H(2)O)(6)}(12){Mo(2)O(4)(HCO(2))}(30)]ca. 200 H(2)O are generated that get filled with water molecules concomitant with an expansion of the three to four shell {H(2)O}(100) cluster. The water shells in both capsules containing different ligands are organized in the form of dodecahedra (partly with underoccupation) and a strongly distorted rhombicosidodecahedron spanned by a {H(2)O}(60)={(H(2)O)(5)}(12) aggregate. The well-defined water shells only emerge if cations cannot enter into the capsules, which is achieved by closing the pores with plugs/guests such as formamidinium cations. The work is based on the syntheses of two new compounds, related single-crystal X-ray diffraction studies, and molecular dynamics simulations, which show remarkably that water molecule shell structuring occurs in the capsules due to the confined conditions even in the case of open pores and at room temperature if cation uptake is prevented.

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mentioning

confidence: 99%

Gated and Differently Functionalized (New) Porous Capsules Direct Encapsulates' Structures: Higher and Lower Density Water

Mitra

Miró

Tomsa

et al. 2009

Chemistry A European J

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“…Therefore, at low temperature the pore would appear more uniformly filled while the walls are less wet and water molecules are arranged in a cubic-ice-like structure. 44 The analogies found between the patterns of the two systems suggest that the features observed for the structure factor at Q ≈ 1.5 Å −1 are related in our case to intra-cluster organization of water molecules within the polymeric matrix. This means, such molecular reorganization would not be directly connected to the above described structural evolution at the inter-cluster and polymer nano-domains levels.…”

Section: Structural Featuresmentioning

confidence: 52%

“…We note that very similar qualitative features and temperature dependence have been reported for water confined in mesoporous MCM-41. 44,45 A combined study of neutron diffraction and empirical potential structure refinement (EPSR) simulations 45 suggested that the mesoscopic arrangement of water molecules in the pore could change as a result of the modified water-water and watersubstrate interactions. Upon cooling, the H-bonds between water molecules would be strengthened, while those between water and the wall atoms become weaker.…”

Section: Structural Featuresmentioning

confidence: 99%

Structure and component dynamics in binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with water and tetrahydrofuran: A diffraction, calorimetric, and dielectric spectroscopy study

Goracci

Arbe

Alegría

et al. 2016

The Journal of Chemical Physics

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We have combined X-ray diffraction, neutron diffraction with polarization analysis, small angle neutron scattering,differential scanning calorimetry, and broad band dielectric spectroscopy to investigate the structure and dynamics of binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with either water or tetrahydrofuran (THF) at different concentrations. Aqueous mixtures are characterized by a highly heterogeneous structure where water clusters coexist with an underlying nano-segregation of main chains and side groups of the polymeric matrix. THF molecules are homogeneously distributed among the polymeric nano-domains for concentrations of one THF molecule/monomer or lower. A more heterogeneous situation is found for higher THF amounts, but without evidences for solvent clusters. In THF-mixtures, we observe a remarkable reduction of the glass-transition temperature which is enhanced with increasing amount of solvent but seems to reach saturation at high THF concentrations. Adding THF markedly reduces the activation energy of the polymer β-relaxation. The presence of THF molecules seemingly hinders a slow component of this process which is active in the dry state. The aqueous mixtures present a strikingly broad glass-transition feature, revealing a highly heterogeneous behavior in agreement with the structural study. Regarding the solvent dynamics, deep in the glassy state all data can be described by an Arrhenius temperature dependence with a rather similar activation energy. However, the values of the characteristic times are about three orders of magnitude smaller for THF than for water. Water dynamics display a crossover toward increasingly higher apparent activation energies in the region of the onset of the glass transition, supporting its interpretation as a consequence of the freezing of the structuralrelaxation of the surrounding matrix. The absence of such a crossover (at least in the wide dynamic window here accessed) in THF is attributed to the lack of cooperativity effects in the relaxation of these molecules within the polymeric matrix.

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“…In the case of AlPO 4 -5, a vertical uptake is observed around P/P 0 = 0.3 without an explicit hysteresis. 46 Thus, we have several questions about water vapor adsorption on the hydrophobic nanoporous solids: What is adsorption hysteresis? Why does hydrophobic porous carbon exhibit hydrophilic behavior?…”

Section: Accommodative Filling Of Water Molecules In Hydrophobic Spacesmentioning

confidence: 99%

Collective Interactions of Molecules with an Interfacial Solid

2012

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Confinement of molecules in nanoscale pores of an interfacial solid such as single wall carbon nanotubes of which all component carbon atoms are exposed to the interface with gas phase induces collective phenomena; the confinement effect is interpreted by the interaction potential theory. The nanoconfinement effect gives rise to in-pore phase anomalies for NO, H 2 O, CCl 4 , superhigh-pressure effect, hydrophobic to hydrophilic transformation for carbon, and a marked quantum molecular sieving. The confinement of KI in the nanotube space below 0.1 MPa produces high-pressure-phase KI above 1.9 GPa. Water molecules gain hydrophilicity with cluster formation in order to accommodate in the hydrophobic carbon spaces. The subnanometer quantum fluctuation for H 2 and D 2 gives rise to a marked quantum molecular sieving effect in nanoscale pores. The Cubased porous coordination polymer crystals can detect the surrounding stimuli such as CO 2 pressure change to vary the crystal lattice, accompanying gate adsorption.

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Confined Water in Mesoporous MCM-41 and Nanoporous AlPO4-5: Structure and Dynamics

Cited by 31 publications

References 15 publications

Gated and Differently Functionalized (New) Porous Capsules Direct Encapsulates' Structures: Higher and Lower Density Water

Gated and Differently Functionalized (New) Porous Capsules Direct Encapsulates' Structures: Higher and Lower Density Water

Structure and component dynamics in binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with water and tetrahydrofuran: A diffraction, calorimetric, and dielectric spectroscopy study

Collective Interactions of Molecules with an Interfacial Solid

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