Characterizing mesoporosity in MOFs: a thermoporometry approach

Abstract

Thermoporometry (TPM) is used to characterize the mesoporosity and, to a certain extent, the macroporosity of materials, offering an alternative to the traditional method of gas physisorption. This study represents the first application of thermoporometry for the evaluation of mesoporous metal–organic frameworks, which have been prepared for a variety of applications. Our investigation focuses on the original MIL-101(Fe)-NH₂ sample, with the most abundant pore sizes determined to be 3.9 and 5.2 nm by TPM. The MIL-101(Fe)-NH₂ variant with an expanded pore size was studied as well, with the pore sizes determined to be 5.1 and 10 nm. The findings demonstrate that thermoporometry utilizing water as the immersion liquid provides results comparable to those obtained by gas (N₂/− 196 °C) physisorption. However, it should be noted that absolute consistency of results cannot be assumed for several reasons, e.g. because of possible volumetric changes in the porosity of the material under study in the wet state.