(598d) Repurposing Organic Structure-Directing Agents for a Priori Control of Chabazite Zeolite Phase and Its Application to Methanol-to-Olefin Reaction

Zeolites are porous aluminosilicate materials used in a variety of industrial applications including acid catalysts, ion-exchange reagents, detergents, and molecular separations. Topological diversity makes zeolites versatile, but also triggers phase competition between multiple metastable polymorphs. This hindered the rational design of the new synthesis routes for zeolites. Recent studies have tried to design new organic structure-directing agents (OSDAs) to crystallize target zeolite framework by predicting the binding energies between the organic molecule and zeolite framework. Yet, there are very few experimental realizations reported from the studies since the computer-designed OSDAs often fail to crystallize the targeted structure or has low synthetic accessibility.

Here, we introduce a novel way to select families of OSDAs for specific zeolite frameworks with the help of computational calculations followed by experimental validations. We made a database containing all the OSDA-zeolite pairs reported in the literature from 1966 to 2020, while calculating the binding energies between the OSDAs and the super cage of the zeolite pores with the force field calculation and DFT methods. Then, potential organic molecules have been introduced in the database to find the relative position compared with the binding energies with previously studied OSDAs so that best promising candidates could be selected. Synthetic accessibility of OSDA candidate molecules was evaluated with the synthetic complexity score.

As a showcase, we present a zeolite framework called Chabazite (CHA) successfully synthesized with a family of OSDAs based on our calculations, which have never been reported to crystallize CHA framework. The new sets of OSDAs can synthesize CHA frameworks without sacrificing the physico-chemical properties compared to the conventional methods and shows excellent performance in methanol-to-olefin reaction. We envision this repurposing OSDA methods can make a breakthrough in zeolite field to select optimal OSDAs for the target zeolite framework more strategically and systematically.