Encapsulation of Pt-based clusters in ZIF-8: Insights from First-Principles Simulations

The reactivity of a Pt-based nanoparticle catalysts greatly depends on their size and detailed atomic structure. Recently, atom-precise nanoparticles have been generated from molecular ligand-stabilized clusters via encapsulation within a metal organic frameworks.^1,2 In this work, we aim to rationalize the underlying encapsulation mechanism of the ligand-stabilized Pt-based using first-principles simulations. Density functional theory (DFT) calculations and ab initio molecular dynamics simulations (AIMD) were carried out to understand the interaction of the Pt-based clusters with the MOF (ZIF-8) precursors in solution. By DFT, we determine the interaction of ZIF-8 precursors with the CO ligands of the Pt-clusters and reveal chemically distinct sites of all the considered clusters which favor the attraction of Zn²⁺ ions in solution. AIMD simulations of Pt-based clusters in an explicit methanol solvent model shed light on the competition between attraction of Zn²⁺ and the Pt-clusters and desorption of Zn²⁺ by solvation with methanol molecules, revealing an importance of bridging CO ligands to create a Zn-rich environment around the Pt-cluster and to guarantee the successful encapsulation.