Institut Charles Gerhardt Montpellier, UMR 5253 CNRS/UM2/ENSCM/UM1, Montpellier, France.
Langmuir. 2012 Jul 31;28(30):11131-41. doi: 10.1021/la3022529. Epub 2012 Jul 19.
The structural, morphological, and adsorption properties of MCM-41 porous silicas are investigated using a realistic numerical model obtained by means of ab initio calculations [Ugliengo, P.; et al. Adv. Mater.2008, 20, 1]. Simulated X-ray diffraction, small angle neutron scattering, and electronic microscopy for the atomistic model are in good agreement with experimental data. The morphological features are also assessed from chord length distributions and porous volume and specific geometrical surface calculations, etc. The N(2), CO(2), and H(2)O adsorption isotherms in the atomistic model of MCM-41 are also in reasonable agreement with their experimental counterpart. An important finding of the present work is that water forms a film adsorbed on specific hydrophilic regions of the surface while the rest of the surface is depleted in water molecules. This result suggests that the surface of MCM-41 materials is heterogeneous, as it is made up of both hydrophilic and hydrophobic patches. While adsorption and irreversible capillary condensation can be described using the thermodynamical approach by Derjaguin (also known as the Derjaguin-Broekhoff-De Boer model), the Freundlich equation fits nicely the data for reversible and continuous filling in small pores.
采用从头计算方法获得的真实数值模型，研究了 MCM-41 多孔硅的结构、形态和吸附性能[Ugliengo, P.;等人。Adv. Mater.2008, 20, 1]。原子模型的模拟 X 射线衍射、小角中子散射和电子显微镜与实验数据吻合良好。形态特征也可以通过弦长分布、多孔体积和特定几何表面积计算等来评估。MCM-41 原子模型中的 N(2)、CO(2)和 H(2)O 吸附等温线也与实验结果相当吻合。本工作的一个重要发现是，水形成吸附在表面特定亲水区域的薄膜，而其余的表面则缺乏水分子。这一结果表明，MCM-41 材料的表面是不均匀的，因为它由亲水和疏水区域组成。虽然吸附和不可逆的毛细凝结可以通过热力学方法（也称为德加古因（Derjaguin）-布罗克豪夫（Broekhoff）-德博尔（De Boer）模型）来描述，但弗伦德利希（Freundlich）方程很好地拟合了小孔隙中可逆和连续填充的实验数据。
