(260b) Study of the Self-Assembly Process of Microporous Materials Using Molecular Modeling

Zeolites are aluminosilicates which are vital in modern technology with applications in fields of catalysis, separations, biosensing and microelectronics. Researchers have synthesized over 200 different type of crystalline frameworks, however only a handful among them have been used commercially. An important research frontier in the field of zeolite science is to understand their formation processes, which would help in fabrication of tailor-made structures for advanced applications. Our research focuses on studying the self-assembly process of such materials using Monte Carlo simulations.

We represent the tetrahedral geometry of silicic acid molecules, building blocks of zeolites, as a unit cell on a body-centerd cubic lattice. In our model a silicon atom occupies the center of a unit cell, whereas the hydroxyl groups are located at the corners. The condensation reaction is modeled as the sharing of hydroxyl groups from two different tetrahedra on the same site, which results in a decrease in total energy. We have applied this model to understand silica polymerization at iso-electric point as well as across pH spectrum, formation of surfactant-templated mesoporous materials, and thermodynamics of stable crystalline states.

Recently, we included structure directing agent molecules to study their effect on the distribution of crystalline states in parallel tempering Monte Carlo simulations. We have systematically studied the effect of size and concentration of the structure directing agent molecules on the properties of the resultant framework. Moreover, to better mimic the synthesis condition, we also applied hyper-parallel tempering Monte Carlo simulations, to gain deeper insights into the self assembly process. We report our progress to date on this research project.