Mecânica Quântica em Ação: Simulando Reações Catalisadas por Zeólitas com o Método ONIOM

Resumo

Hybrid quantum mechanical/molecular mechanical (QM/MM) methods have become essential tools for
studying complex systems, particularly when a full quantum mechanical treatment is computationally
prohibitive. This work provides a comprehensive overview of hybrid modeling approaches, with an
emphasis on the ONIOM method, and explore their applications in catalysis. Based on detailed studies
of zeolite-catalyzed reactions, including the formation and stabilization of tert-butyl and bicyclobutonium
cations, we demonstrate how hybrid methods enable an accurate description of reaction mechanisms,
intermediates, and transition states while maintaining computational efficiency. The results show that
the ONIOM approach successfully describes important effects such as spatial confinement, electrostatic
stabilization, and dispersion interactions within zeolite framework. These findings highlight the role of
zeolites as “solid solvents”, capable of inducing substrate ionization and stabilizing ionic species in a
manner analogous to polar solvents. Furthermore, we investigate the influence of ionic pairs, such as Na⁺Cl^–, on carbocation stability, showing that hybrid approaches can effectively capture periodic electrostatic
effects. This study emphasizes the importance of multiscale modeling techniques in the rational design
of catalysts and in understanding reactivity at the molecular level.
Keywords: Hybrid methods; QM/MM; ONIOM; zeolites; heterogeneous catalysis; carbocations.