Abstract: Using the sol–gel method, by reacting solutions of maleic acid and potassium permanganate, samples have been obtained with a turbostat stacking of layers, which is characteristic of the birnessite structure. Using X-ray phase and thermogravimetric analysis, Raman spectroscopy, and low-temperature nitrogen adsorption, the dependence of the textural–structural characteristics of the synthesized materials on the temperature of thermal modification (150, 360°C) and sample composition (Sr-form, H-form) has been shown. It has been found that all samples are characterized by a mesoporous texture. It is shown that the water content in the samples is closely related to the quantitative determination of the specific surface area: the more water, the greater the S BET value. © 2023, Pleiades Publishing, Ltd.