@article {637, title = {Adsorption in heterogeneous porous media: Hierarchical and composite solids}, journal = {Microporous and Mesoporous Materials}, volume = {229}, year = {2016}, month = {Jul-15-2016}, pages = {145 - 154}, abstract = {

Experiment and molecular simulation are used to investigate adsorption in heterogeneous porous media consisting of hierarchical solids (combining different porosity scales) or composite solids (such as silver nanoparticles adsorbed at the external surface of zeolite). It is shown that adsorption in such heterogeneous materials can be written as a linear combination of the adsorption isotherms in its different domains (i.e. porosity scales for the hierarchical sample and constituents for the composite sample). In the case of the composite material, we also show that the linear combination can be used with weighing parameters obtained for a different adsorbate. Such a superimposition principle, which is validated using well-characterized experimental samples, is of interest for characterization purpose as well as industrial applications as they can be used to determine accurately the amount of phases in a given sample (volume corresponding to a given porosity scale or constituent). In contrast, significant departure between the experimental adsorption isotherm and the linear combination can be used to detect coupling effects between the different domains or restrained access to a given domain type. Such a characterization strategy of complex heterogeneous media is complementary to other experiments, such as those probing capillary hysteresis shapes, scanning curves and subloops, which allow determining the distribution of domains within the framework of the independent domain theory. (C) 2016 Elsevier Inc. All rights reserved.

}, issn = {13871811}, doi = {10.1016/j.micromeso.2016.04.011}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1387181116301032}, author = {Deliere, Ludovic and Fran{\c c}ois Villemot and David Farrusseng and Anne Galarneau and Topin, Sylvain and Benoit A. Coasne} } @article {641, title = {Probing Interconnectivity in Hierarchical Microporous/Mesoporous Materials Using Adsorption and Nuclear Magnetic Resonance Diffusion}, journal = {The Journal of Physical Chemistry C}, volume = {120}, year = {2016}, month = {Jan-28-2016}, pages = {1562-1569}, abstract = {

Adsorption and transport in hierarchical materials are investigated by means of adsorption and nuclear magnetic resonance experiments. Using micro/mesoporous zeolites with well-defined mesoporosity, we show that adsorption at a given pressure can be described as a simple linear combination of the adsorbed amounts taken at the same pressure for the pure microporous (zeolite FAU-Y) and mesoporous (Al-MCM-41) solids. Such a quantitative decomposition allows us to demonstrate the ability of diffusion measurements by Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR) to probe interconnectivity in hierarchical solids. On the one hand, transport in the mechanical mixtures can be described as the superimposition of diffusion in pure microporous and mesoporous solids. On the other hand, PFG NMR for the hierarchical sample provides an effective diffusivity that is intermediate between those for the pure zeolite and mesoporous silica. Furthermore, this effective diffusivity is slower than the linear combination of the two diffusivities weighted by the number of molecules present in each phase (used in the independent domain and fast-exchange theories) clearly showing interconnectivities and transfer limitations between the microporous and mesoporous domains. We also discuss the ability of combining theories such as the fast exchange model and the effective medium theory to quantitatively predict diffusion in such microporous/mesoporous materials.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.5b10129}, url = {http://pubs.acs.org/doi/10.1021/acs.jpcc.5b10129}, author = {Anne Galarneau and Guenneau, Flavien and Gedeon, Antoine and Mereib, Diaa and Rodriguez, Jeremy and Fajula, Fran{\c c}ois and Benoit A. Coasne} } @article {179, title = {Advances in design and modeling of porous materials}, journal = {The European Physical Journal Special Topics}, volume = {224}, year = {2015}, month = {Jul-2015}, pages = {1653 - 1653}, abstract = {

This special issue of the European Physical Journal Special Topics is dedicated to selected papers from the symposium \“High surface area porous and granular materials\” organized in the frame of the conference \“Mat\ériaux 2014\”, held on November 24\–28, 2014 in Montpellier, France.

Porous materials and granular materials gather a wide variety of heterogeneous, isotropic or anisotropic media made of inorganic, organic or hybrid solid skeletons, with open or closed porosity, and pore sizes ranging from the centimeter scale to the sub-nanometer scale. Their technological and industrial applications cover numerous areas from building and civil engineering to microelectronics, including also metallurgy, chemistry, health, waste water and gas effluent treatment. Many emerging processes related to environmental protection and sustainable development also rely on this class of materials. Their functional properties are related to specific transfer mechanisms (matter, heat, radiation, electrical charge), to pore surface chemistry (exchange, adsorption, heterogeneous catalysis) and to retention inside confined volumes (storage, separation, exchange, controlled release). The development of innovative synthesis, shaping, characterization and modeling approaches enables the design of advanced materials with enhanced functional performance. The papers collected in this special issue offer a good overview of the state-of-the-art and science of these complex media.

We would like to thank all the speakers and participants for their contribution to the success of the symposium. We also express our gratitude to the organization committee of \“Mat\´eriaux 2014\”. We finally thank the reviewers and the staff of the European Physical Journal Special Topics who made the publication of this special issue possible.

}, issn = {1951-6355}, doi = {10.1140/epjst/e2015-02487-6}, author = {Ayral, Andre and Calas-Etienne, Sylvie and Benoit A. Coasne and Deratani, Andr{\'e} and Evstratov, Alexis and Anne Galarneau and Grande, Daniel and Hureau, Matthieu and Jobic, Herv{\'e} and Morlay, Catherine and Parmentier, Julien and Prelot, B{\'e}n{\'e}dicte and Rossignol, Sylvie and Simon-Masseron, Ang{\'e}lique and Thibault-Starzyk, Fr{\'e}d{\'e}ric} } @article {176, title = {Control of the Pore Texture in Nanoporous Silicon via Chemical Dissolution}, journal = {Langmuir}, volume = {31}, year = {2015}, month = {Jul-28-2015}, pages = {8121 - 8128}, abstract = {
Abstract Image

The surface and textural properties of porous silicon (pSi) control many of its physical properties essential to its performance in key applications such as optoelectronics, energy storage, luminescence, sensing, and drug delivery. Here, we combine experimental and theoretical tools to demonstrate that the surface roughness at the nanometer scale of pSi can be tuned in a controlled fashion using partial thermal oxidation followed by removal of the resulting silicon oxide layer with hydrofluoric acid (HF) solution. Such a process is shown to smooth the pSi surface by means of nitrogen adsorption, electron microscopy, and small-angle X-ray and neutron scattering. Statistical mechanics Monte Carlo simulations, which are consistent with the experimental data, support the interpretation that the pore surface is initially rough and that the oxidation/oxide removal procedure diminishes the surface roughness while increasing the pore diameter. As a specific example considered in this work, the initial roughness \ξ \∼ 3.2 nm of pSi pores having a diameter of 7.6 nm can be decreased to 1.0 nm following the simple procedure above. This study allows envisioning the design of pSi samples with optimal surface properties toward a specific process.

}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.5b01518}, author = {Secret, Emilie and Wu, Chia-Chen and Chaix, Arnaud and Anne Galarneau and Gonzalez, Philippe and Cot, Didier and Sailor, Michael J. and Jestin, Jacques and Zanotti, Jean-Marc and Cunin, Fr{\'e}d{\'e}rique and Benoit A. Coasne} } @article {108, title = {Adsorption and Dynamics in Hierarchical Metal-Organic Frameworks}, journal = {Journal of Physical Chemistry C}, volume = {118}, year = {2014}, month = {Apr-10-2014}, pages = {7423-7433}, type = {Article}, abstract = {

Adsorption and dynamics in hierarchical metal-organic frameworks are investigated by means of molecular simulation. The models of hierarchical porous solids are obtained by carving mesopores of different diameters out of a crystal of Cu-BTC (model A) or by inserting a microporous particle of Cu-BTC in an amorphous silica mesopore (model B). We show that the nitrogen adsorption isotherms at 77 K for the solids corresponding to model A can be described as a linear combination of reference adsorption isotherms for pure microporous and mesoporous solids. In contrast, the adsorption isotherms for model B cannot be described accurately as a sum of reference microporous and mesoporous adsorption isotherms. The inserted particle acts as a constriction which helps nucleate the liquid phase within the mesopore so that no capillary condensation hysteresis is observed. The dynamics of nitrogen adsorbed at 77 K inside the porosity of the hierarchical solids is also investigated. The Fickian regime is reached at long times which are not attainable with molecular dynamics simulations. At higher temperature, the faster self-diffusion makes it possible to obtain the diffusivity of the adsorbate. Nitrogen adsorbed in the microporosity of the hierarchical porous solids has a self-diffusion coefficient close to that of nitrogen adsorbed in pure Cu-BTC. In contrast, diffusion in the mesoporosity is faster than in the microporosity so that the overall diffusivity is faster than in pure Cu-BTC.

\<\>Abstract Image

}, issn = {1932-7447}, doi = {10.1021/jp500037z}, author = {Fran{\c c}ois Villemot and Anne Galarneau and Benoit A. Coasne} } @article {64, title = {Adsorption-based characterization of hierarchical metal{\textendash}organic frameworks}, journal = {Adsorption}, volume = {20}, year = {2014}, month = {Feb-2014}, pages = {349-357}, abstract = {

Nitrogen adsorption at 77 K on metal\–organic framework (MOF) is investigated by means of molecular simulations. We consider both regular Cu\–BTC crystal and a MOF-based hierarchical porous solid consisting of a mesopore carved out of a Cu\–BTC crystal. The t-plot method is applied to these solids by using a non-porous Cu\–BTC surface as the reference sample. The values of the mesoporous and external surface areas are determined from the t-plot, and the validity of the method for this type of hierarchical solid is discussed.

}, keywords = {Adsorption, Hierarchical porous materials, Molecular simulation, t-Plot}, issn = {0929-5607}, doi = {10.1007/s10450-013-9583-7}, author = {Fran{\c c}ois Villemot and Anne Galarneau and Benoit A. Coasne} } @article {92, title = {Validity of the t-plot Method to Assess Microporosity in Hierarchical Micro/Mesoporous Materials}, journal = {Langmuir}, volume = {30}, year = {2014}, month = {Nov-2014}, pages = {13266-13274}, type = {Article}, abstract = {
Abstract Image

The t-plot method is a well-known technique which allows determining the micro- and/or mesoporous volumes and the specific surface area of a sample by comparison with a reference adsorption isotherm of a nonporous material having the same surface chemistry. In this paper, the validity of the t-plot method is discussed in the case of hierarchical porous materials exhibiting both micro- and mesoporosities. Different hierarchical zeolites with MCM-41 type ordered mesoporosity are prepared using pseudomorphic transformation. For comparison, we also consider simple mechanical mixtures of microporous and mesoporous materials. We first show an intrinsic failure of the t-plot method; this method does not describe the fact that, for a given surface chemistry and pressure, the thickness of the film adsorbed in micropores or small mesopores (\< 10\σ, \σ being the diameter of the adsorbate) increases with decreasing the pore size (curvature effect). We further show that such an effect, which arises from the fact that the surface area and, hence, the free energy of the curved gas/liquid interface decreases with increasing the film thickness, is captured using the simple thermodynamical model by Derjaguin. The effect of such a drawback on the ability of the t-plot method to estimate the micro- and mesoporous volumes of hierarchical samples is then discussed, and an abacus is given to correct the underestimated microporous volume by the t-plot method.

}, issn = {0743-7463}, doi = {10.1021/la5026679}, author = {Anne Galarneau and Fran{\c c}ois Villemot and Rodriguez, Jeremy and Fajula, Fran{\c c}ois and Benoit A. Coasne} } @article {95, title = {Adsorption, intrusion and freezing in porous silica: the view from the nanoscale}, journal = {Chemical Society Reviews}, volume = {42}, year = {2013}, month = {Jan-24-2013}, pages = {4141-4171}, type = {Review}, abstract = {

This review presents the state of the art of molecular simulation and theory of adsorption, intrusion and freezing in porous silica. Both silica pores of a simple geometry and disordered porous silicas which exhibit morphological and topological disorders are considered. We provide a brief description of the numerical models of porous silicas available in the literature and present the most common molecular simulation and theoretical methods. Adsorption in regular and irregular pores is discussed in the light of classical theories of adsorption and capillary condensation in pores. We also present the different evaporation mechanisms for disordered systems: pore blocking and cavitation. The criticality of fluids confined in pores, which is still the matter of debate, is then discussed. We review theoretical results for intrusion/extrusion and freezing in silica pores and discuss the validity of classical approaches such as the Washburn-Laplace equation and Gibbs-Thomson equation to describe the thermodynamics of intrusion and in-pore freezing. The validity of the most widely used characterization techniques is then discussed. We report some concluding remarks and suggest directions for future work.

Graphical abstract: Adsorption, intrusion and freezing in porous silica: the view from the nanoscale

}, issn = {0306-0012}, doi = {10.1039/c2cs35384a}, author = {Benoit A. Coasne and Anne Galarneau and Roland Jean-Marc Pellenq and Di Renzo, Francesco} } @article {81, title = {Adsorption-based characterization of hierarchical metal-organic frameworks}, journal = {Adsorptio-Journal of the International Adsorption Society}, volume = {20}, year = {2013}, month = {Oct-06-2013}, pages = {349-357}, type = {Article}, abstract = {

Nitrogen adsorption at 77 K on metal-organic framework (MOF) is investigated by means of molecular simulations. We consider both regular Cu-BTC crystal and a MOF-based hierarchical porous solid consisting of a mesopore carved out of a Cu-BTC crystal. The t-plot method is applied to these solids by using a non-porous Cu-BTC surface as the reference sample. The values of the mesoporous and external surface areas are determined from the t-plot, and the validity of the method for this type of hierarchical solid is discussed.

}, keywords = {Adsorption, Hierarchical porous materials, Molecular simulation, t-Plot}, issn = {0929-5607}, doi = {10.1007/s10450-013-9583-7}, author = {Fran{\c c}ois Villemot and Anne Galarneau and Benoit A. Coasne} } @article {34, title = {Molecular simulation of adsorption and transport in hierarchical porous materials}, journal = {Langmuir}, volume = {29}, year = {2013}, month = {May-29-2013}, pages = {7864{\textendash}7875}, abstract = {

\<\>Abstract Image

Adsorption and transport in hierarchical porous solids with micro- (\∼1 nm) and mesoporosities (\>2 nm) are investigated by molecular simulation. Two models of hierarchical solids are considered: microporous materials in which mesopores are carved out (model A) and mesoporous materials in which microporous nanoparticles are inserted (model B). Adsorption isotherms for model A can be described as a linear combination of the adsorption isotherms for pure mesoporous and microporous solids. In contrast, adsorption in model B departs from adsorption in pure microporous and mesoporous solids; the inserted microporous particles act as defects, which help nucleate the liquid phase within the mesopore and shift capillary condensation toward lower pressures. As far as transport under a pressure gradient is concerned, the flux in hierarchical materials consisting of microporous solids in which mesopores are carved out obeys the Navier\–Stokes equation so that Darcy\’s law is verified within the mesopore. Moreover, the flow in such materials is larger than in a single mesopore, due to the transfer between micropores and mesopores. This nonzero velocity at the mesopore surface implies that transport in such hierarchical materials involves slippage at the mesopore surface, although the adsorbate has a strong affinity for the surface. In contrast to model A, flux in model B is smaller than in a single mesopore, as the nanoparticles act as constrictions that hinder transport. By a subtle effect arising from fast transport in the mesopores, the presence of mesopores increases the number of molecules in the microporosity in hierarchical materials and, hence, decreases the flow in the micropores (due to mass conservation). As a result, we do not observe faster diffusion in the micropores of hierarchical materials upon flow but slower diffusion, which increases the contact time between the adsorbate and the surface of the microporosity.

}, doi = {10.1021/la401228k}, author = {Benoit A. Coasne and Anne Galarneau and Gerardin, Corine and Fajula, Fran{\c c}ois and Fran{\c c}ois Villemot} }