Estimation of Neck Size Distribution in Ordered Cagelike Materials Using Nitrogen and Water Desorption Isotherms

Abstract

To estimate the neck size distributions in ordered cagelike materials KIT-5 with prolonged hydrothermal treatments, we measured the desorption isotherms of water at 293 K on the cagelike materials and then calculated the desorption isotherms of nitrogen at 77 K and water at 293 K based on the model pore networks with normal distributions of neck sizes that mimic the pore structure of KIT-5. First, it was found that the position of the desorption isotherms does not at all reflect the mean size of necks unless the width of the neck size distribution is fixed, and thus the simple analysis of the desorption isotherms in the absence of networking effects leads to erroneous distribution of neck sizes. The gradual desorption isotherms of nitrogen and water observed for KIT-5 samples were not well reproduced based on the model pore networks with no correlation in the spatial distribution of neck sizes. On the other hand, inclusion of correlation in the spatial distribution of neck sizes led to exceedingly better ...