Rational Design of Organic Structure-Directing Agents\nfor AFX Zeolite Synthesis from Molecular Mechanics and Molecular Dynamics

Molecular mechanics calculations\nand molecular dynamics (MD) simulations\nbased on force fields are used to measure the interactions between\norganic cations and AFX. The lowest-energy organic structure-directing\nagent (OSDA)–AFX structures are obtained by using the simulated\nannealing combined with MD, and the binding energies of 81 organic\ncations to AFX are calculated. It is found that the chemical properties\nof the organic cations play a minor role in determining the binding\nenergies, which are determined largely by the relative molecular masses\nof the organic cations. The calculated deformation energies of the\norganic cations indicate that a more negative binding energy does\nnot necessarily imply that the organic cation better fits the zeolite\npore. With 19 organic cations validated by available experimental\nobservations, another 16 organic cations that can be synthesized and\nare found to have comparable or more negative binding energies as\nwell as relatively small deformation energies are newly proposed\nas potential OSDA candidates.