Mechanistic understanding of material synthesis

Structure directing agents (SDAs) influence not only zeolite structure but also the distribution of Al on zeolite lattices. The origins of this Al directing influence are not well understood. Here, we use first-principles methods to explore the interactions be- tween an N,N,N-trimethyl-1-adamantyl ammonium (TMAda⁺) OSDA and framework [AlO₂ ]^– within an SSZ-13 lattice. Molecular dynamics and geometric and electronic structures illuminate the rotational freedom of TMAda⁺ OSDA within an SSZ-13 cage, the primarily electrostatic nature of its interactions with [AlO₂]^–, and the relative in- variance of that interaction within a subset of Al locations within the same SSZ-13 major cavity. These results indicate Al distribution patterns observed in relevant SSZ- 13 samples are not consequences of location bias for Al substitution within a single TMAda⁺−cage complex. Further study shows that long-range electrostatics among multiple TMAda⁺−cage complexes is relevant and the electrostatics can be altered by introducing alkali ions into the synthetic gel. The computational protocol reported here provide guidance of incisive control of Al distribution in SSZ-13 and can be employed generally to examine other combinations of SDAs and zeotypes of interest.

• Related Paper

Influence of N,N,N-trimethyl-1-adamantyl ammonium structure directing agent on Al siting in SSZ-13 zeolite

S. Li , R. Gounder, A. Debellis, I. B. Mueller, S. Prasad, A. Moini and W. F. Schneider*. Under peer review

Cooperation and Competition Between Organic and Inorganic Structure Directing Agents Influences the Aluminum Arrangement in CHA Zeolites

J. R. Di Iorio#, S. Li#, (#equal contribution) C. B. Jones, E. Kunkes, S. Prasad, A. Moini, W. F. Schneider and R. Gounder*. Submitted

• Example video illustrating TMAda⁺ dynamics

• Related Poster

2018 BASF North American Research Forum , Iselin, NJ (click the poster for high-resolution file)