Imaging of Gas Molecules Adsorbed in the Mesoporous Material by the High Brilliance Synchrotron Powder Diffraction.

介孔材料是在原子尺度上没有有序结构的无定形材料。无定形形成介观尺度的孔结构。迄今为止，通过电子晶体学或X射线衍射研究了介孔的排列和粗糙形状。但没有发现中孔吸附分子的信息。利用高亮度同步辐射粉末衍射实验和最大熵方法（MEM），对吸附在介孔中的分子进行结构信息的研究，并利用尺寸、密度等参数解析地描述了具有一维介孔的MCM-41的介孔形状。通过比较模拟结果和实际观察到的衍射强度，揭示了焙烧前后介孔尺寸和形状的变化。对具有三维介孔的MCM-48进行了气体吸附的原位同步辐射粉末衍射实验，对于不含客体分子的数据，通过常规方法获得的粗糙孔形状和从等温线估计的孔体积的组合使得我们能够缩放结构因子。利用微机电成像技术成功地对介孔结构进行了成像，得到了清晰的介孔电子密度分布图像，并发现迄今为止对介孔的尺寸估计不足。该技术可用于分析更复杂的孔表面网络和精细结构，并可通过电子密度的变化观察气体吸附过程。获得了气体吸附过程的结构信息，即低压区的单层吸附状态、临界压力区的毛细凝聚状态和饱和吸附状态。虽然对于相的处理需要进行检查，但是该技术作为气体吸附状态的观察技术预期是有效的。

Mesoporous materials are amorphous materials without ordered structure on an atomic scale. The amorphous forms the pore structure of a meso scale. The arrangement and the rough shape of mesopores were investigated by the electron crystallography or X-ray diffraction to date. But no information on molecules adsorbed in the mesopore was revealed. The purpose of this research is to obtain the structural information of molecules adsorbed in the mesopores by the high brilliance synchrotron powder diffraction experiment and the maximum entropy method (MEM).The shape of mesopore of MCM-41 with a one-dimensional mesopore was analytically expressed using parameters of size, density, etc.. Comparing the simulated and observed diffraction intensities revealed the change of the size and shape of mesopores before and after calcination.The in-situ synchrotron powder diffraction experiment of gas adsorption was performed for MCM-48 with a three-dimensional mesopore.For the data without guest molecules, the combination of rough pore shape obtained by the conventional method and the pore volume estimated from the isotherm enabled us to scale the structure factors. The mesopore structure was successfully imaged by MEM. The MEM electron density distribution showed clear image and the size of the mesopore was found to be underestimated to date. This technique would be effective for the analysis of more complicated network and fine structure of pore surfaces.The gas adsorption process was observed as the change of electron density. The structural information on the gas adsorption process was able to be obtained, that is, the mono-layer adsorption state in the low pressure region, the capillary condensation in threshold value of pressure and the saturation adsorption state. Although the examination should be required for the treatment of phases, this technique is expected to be effective as the observation technique of a gas adsorption state.