8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.16Thu 811:10-14:00Adsorption and dynamics of molecules in hierarchicalnanoporous materialsBenoit Coasne, 1 Robin Chal, 1 Anne Galarneau, 1 and Corine Gerardin 11 CNRS - Institut Charles Gerhardt Montpellier, 8 rue de l Ecole Normale, 34096,Montpellier, FranceSignificant efforts have been devoted to design and synthesize hierarchical porous materials combiningdifferent porosities. These solids exhibit 1) a large surface area of ”active sites” in thesmallest porosity scale and 2) a high permeability and access to these sites that arises from theefficient (less restricted) transport in the largest porosity scale. Hierarchical solids include microporouszeolite nanocrystals (pores < 2 nm) assembled into mesoporous structures (pores > 2nm) or zeolite microporous crystals in which mesopores are introduced. While the benefits of includingseveral porosity scales have been demonstrated, some uncertainties remain regarding thebehavior of adsorbates in hierarchical solids. Molecular modeling is an efficient tool to investigatethe adsorption and dynamics of adsorbates in hierarchical solids. It allows 1) clarifying the roleof the connections between the different porosities on the adsorbate properties and 2) studying towhich extent the two porosities can be considered as independent subsystems: is the adsorption ordynamics in the solid the sum of the data in the small and large porosity scales? In this work, wereport a model of hierarchical solids consisting of a mesoporous silica with zeolitic walls modeledon H-faujasite. We then investigate by means of Monte Carlo and Molecular Dynamics simulationsthe adsorption and dynamics of nitrogen in this realistic model. By comparing with resultsfor pure microporous and mesoporous materials, we show that the microporosity in the walls ofthe mesoporous material affects the mesopore filling. Emphasis will be also paid to the dynamicsat the junction between the two types of porosity. The present simulations provide a theoreticalbasis for the interpretation of experimental data in hierarchical porous solids.16