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Bicontinuous nanoporous materials are desirable for catalysis, storage, and separation applications. Self-assembly or phase separation of organic polymers is the general route to the structure. However, the three-dimensionally continuous organic nanostructure with a large interface area has low thermal stability and solvent resistance, limiting its applicability under various chemical environments. Here, we show a direct solution-casting preparation of a bicontinuous nanoporous membrane by utilizing the combination of phase separation, gelation, and polymerization, which occurred sequentially with the evaporation of solvent from the sol mixture of a polyurea network nanogel particle and an alkoxysilane derivative. The single evaporation process yielded a thin-film membrane with a three-dimensional reticulated nanoporous structure composed of a continuous polyurea network skeleton coated with an organosilica shell. Despite the broad pore size distribution in the 5−70 nm range, ultrafiltration through the bicontinuous conduit exhibited a sharp molecular weight cutoff near 6 nm, close to the lower limit of the pore size range. The unique filtration behavior of the bicontinuous nanoporous hybrid frameworks using the scalable and straightforward method of preparation is promising for the removal of nanoparticulate contaminants in liquids, for example, viruses in downstream processing. The porous hybrid materials of different organic−inorganic combinations may be synthesized by employing a similar approach.

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Copolyurea networks (co-UNs) were synthesized via crosslinking polymerization of a mixture of tetrakis(4-aminophenyl)methane (TAPM) and melamine with hexamethylene diisocyanate (HDI) using the organic sol-gel polymerization method. The subsequent thermal treatment of between 200 and 400 °C induced the sintering of the powdery polyurea networks to form porous frameworks via urea bond rearrangement and the removal of volatile hexamethylene moieties. Incorporating melamine into the networks resulted in a higher nitrogen content and micropore ratio, whereas the overall porosity decreased with the melamine composition. The rearranged network composed of the tetraamine/melamine units in an 80:20 ratio showed the highest carbon dioxide adsorption quantity at room temperature. The results show that optimizing the chemical structure and porosity of polyurea-based networks can lead to carbon dioxide adsorbents working at elevated temperatures.