Two-Dimensional MFI Zeolite Nanosheets Exfoliated by Surfactant Assisted Solution Process

Two-dimensional (2D) zeolite nanosheets are important for the synthesis of high flux zeolite membranes due to their lateral size in a preferred orientation. A way to obtain 2D zeolite nanosheets is to exfoliate interlocked structures generated during the hydrothermal synthesis. The mechanical and polymer assisted exfoliation process leads to mechanical damage in nanosheets and short lateral size. In the present study, polyvinylpyrrolidone (PVP) was introduced as an exfoliation agent and dispersant, so that multilamellar interlocked silicalite-1 zeolite nanosheets successfully exfoliated into a large lateral size (individual nanosheets 500 similar to 1200 nm). The good exfoliation behavior was due to the strong penetration of PVP into multilamellar nanosheets. Sonication assisted by mild milling helps PVP molecules to penetrate through the lamellar structure, contributing to the expansion of the distance between adjacent layers and thus decreasing the interactions between each layer. In addition, the stability of exfoliated nanosheets was evaluated with a series of organic solvents. The exfoliated nanosheets were well dispersed in n-butanol and stable for 30 days. Therefore, the PVP-assisted solution-based exfoliation process provides high aspect ratio MFI zeolite nanosheets in organic solvents for a long period.

Automated summary

In this study, polyvinylpyrrolidone (PVP) was introduced as an exfoliation agent and dispersant to successfully exfoliate multi-layered interlocked silicalite-1 zeolite nanosheets into large lateral sizes. The strong penetration of PVP into the multi-lamellar nanosheets, assisted by sonication and mild milling, contributed to the expansion of the distance between layers and decreased interactions. The stability of the exfoliated nanosheets in organic solvents was confirmed, with good dispersion and stability in n-butanol for 30 days.