One-Pot Single-Step Route toward Bicontinuous Nanoporous Membranes of an Organic-Inorganic Core-Shell Network

Abstract

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.