There is a strong demand for selective capture and storage of radioactive fission products, of which iodine-129 (129I) is one of the most problematic radioisotopes due to its long half-life of 1.57 × 107 years. Selective chemical adsorption of radioactive iodine (I2 or RI) requires nanoporous solid sorbents. Most studies note that iodine adsorption is physical, despite its preference only for reused materials. Since the stability of materials decreases during physical sorption, the regenerability of adsorbents conflicts with their long-term stability. Therefore, for the adsorption of iodine, solid porous bodies with surface functional groups are developed, which can interact with iodine chemically when chemical stability is required, although the sorption capacity is reduced. A reliable option is mesostructured silica materials, which provide both stability and high capture capacity. Irreversible iodine uptake can be achieved by its chemisorption in the pore space of bismuth-modified mesoporous silica materials. In this case, the absorption of iodine with the formation of a Bi-I chemical bond in the pores filled with the resulting compound simulates the process of physical sorption. The purpose of this work is to study the adsorption and structural properties of ordered mesoporous bismuthosilicate deposited by the alkoxide sol-gel method from tetraethoxysilane in an acidic medium on a block copolymer of polyoxyethylene and polyoxypropylene, Sunperonic F108. Despite reports on the prospects of using Bi-SBA-15 materials in the adsorption of iodine gas, the method for self-assembly of bismuth-substituted silica nanoparticles remains open. In this work, bismuth-substituted plugged hexagonally templated silica (PHTS) was synthesized at Bi/Si molar ratios of 1/99 and 5/95. It is a composite material, an analogue of SBA-15, consisting of fairly large homogeneous mesopores containing microporous nanoparticles in the form of plugs in mesopore channels. The measured nitrogen sorption isotherms are Type IV, according to the IUPAC classification, have an H5 Hysteresis loop and demonstrate single-step capillary condensation, indicating the filling of homogeneous mesopores. with two-stage desorption [1]. The resulting material demonstrates a bimodal size distribution of mesopores, a controlled number of open and clogged mesopores, has thickened pore walls (≈ 3 nm), “perforated” by micropores, which leads to large surface areas of micropores (up to 230 m2/ g). The combined micro- and mesoporosity, high stability, and ability to control the texture and morphological characteristics of bismuth-substituted silica may be useful in the selective chemical adsorption of radioactive iodine.