Assembly of Zeolitic Crystals From a Model of Mesogenic Patchy Nanoparticles

Abstract

Porous zeolitic crystals made of nanoparticles could have interesting applications in membranes and photonics. However, there is not yet a synthetic pathway to realize these complex architectures using nanoparticles. The challenge arises from the difficulty to control independently the different length scales intrinsic to the ordering of zeolitic crystals: the short-range tiling of the typically tetravalent sites that form the crystal, and the medium-and long-range order and connectivity of the pores. Here we propose a strategy to nucleate and grow zeolitic crystals from a binary mixture of nanoparticles in which one component favors tetravalent coordination and the two types of particles interact through frustrated attraction that promotes the formation of mesophases. We use molecular simulations to demonstrate that this approach produces zeolitic crystals in which the ordering of the pores is controlled by the structure of the mesophase, while the tiling of the network-former particles is controlled by the strength of orientational interactions of the model patchy particles. We investigate the formation of two gyroidal zeolitic crystals and the transformations between them to elucidate the role of the mesophases in the crystallization, polymorph selection, and crystal-tocrystal transformations between zeolitic crystals. This study provides a novel and distinct avenue to assemble porous zeolitic crystals from mesogenic patchy nanoparticles.

Coarse-Grained Model for the Hydrothermal Synthesis of Zeolites

“…Despite its simplicity, the TS–Z model spontaneously nucleates various zeolites at cooling rates accessible to molecular simulations . The binary mixture of the dry model with x T = 0.74 spontaneously nucleates zeolite Z1 (Figure a,b), which has the same structure of the FIR-30 metal–organic framework. , The silica-like T particles in zeolite Z1 tile a double-gyroid surface with an I 4 1 32 symmetry that encloses two interpenetrated helical channels filled with ordered S particles . Z1 has 10-member ring channels, the same as silicalite-1 .…”

“…Z1 has 10-member ring channels, the same as silicalite-1 . The channels are tiled with squares and pentagons and meet in 12-member ring cavities. , …”

“…Q 3 does not fall to 0 in the zeolite because ∼15% of the silica sites in the perfect Z1 crystal are threecoordinated. 62 In the experiments 103,104 as well as in the simulations, the development of crystallinity is accompanied by an evolution of the silica rings toward the ones in the zeolite. The population of rings in the amorphous phase is broader than that in the zeolites in both our simulations (Figure 9d) and the experiments.…”

“…86 The channels are tiled with squares and pentagons and meet in 12-member ring cavities. 60,62 In the present study, we combine the binary TS−Z with λ = 4 zeolite-former model 61 with the monatomic model of water mW 65 into a three-component TS + W model that represents the polymerization, crystallization, and dehydration transitions that are characteristic of HS of zeolites. We model the interactions of mW water with T and S using the two-body component of the SW potential.…”

“…More recently, Molinero and co-workers developed simple coarse-grained (CG) models − that nucleate and grow zeolites in molecular dynamics simulations. − These models represent the silica-like tetrahedral network former T as a single particle that interacts with other T through a combination of two- and three-body interactions that favor angles of silica, and the SDA as a single particle S that interacts with S and T through two-body potentials. − Modeling silica as a single particle, without explicit oxygen atoms, allows for the reconstruction of the network in simulations without the need to introduce explicit barriers or moves to account for the hydrolysis and condensation reactions. Despite the ability of these simple models to nucleate and grow a variety of zeolites, they are not known to model correctly the polymerization of silica, and they do not quantitatively reproduce the experimental speciation of silicate species in the amorphous phase from which the zeolites form …”