Comparative study of lattice parameter and pore size of ordered mesoporous silica materials using physisorption, SAXS measurements and transmission electron microscopy

A precise knowledge of the structural properties of ordered mesoporous materials is essential for their use in almost every application. Researchers use various methods, based on transmission electron microscopy, physisorption and scattering experiments to obtain this data. Here, we evaluate and compare the different methods for four different mesoporous silica materials with pore sizes ranging from 3 to 11 nm. We use the commonly applied methods of physisorption to measure the pore size, fitting of small-angle X-ray scattering data to obtain both the pore size and the lattice parameter, and estimate the lattice parameter from transmission electron micrographs. Besides this, we extract information about the pore sizes from electron density maps. We perform a comparative analysis of the different methods as well as discuss their advantages and disadvantages. We find that all methods deliver comparable results over the investigated pore size range and thus are interchangeable. The only exception is the evaluation of physisorption data of very small mesopores with the BJH method, which does not provide meaningful results.