Extended Data Fig. 10: Periodic DFT computations for the PDH steps over Pt–Sn2 monomers and (Pt–Sn2)2 dimers confined within the MFI framework.
From: Pt migration–lockup in zeolite for stable propane dehydrogenation catalyst
Geometries of initial (IS), transitional (TS) and final (FS) states for the dehydrogenation of propane (a), propyl isomer (b), propylene (c) and H2 (d) formation over Pt–Sn2 monomers within S-1. Geometries of IS, TS and FS for the dehydrogenation of propane (e), propyl isomer (f), propylene (g) and H2 (h) formation over (Pt–Sn2)2 dimers within S-1. Geometries of IS, TS and FS for the dehydrogenation of propane (i), propyl isomer (j), propylene (k) and H2 (l) formation over (Pt–Sn2)2 dimers with the formation of Pt–Si and Pt–O bonds with framework (named (Pt–Sn2)2*). m, Energy profiles for dehydrogenation of propane to propylene and coke precursor and H2 formation on Pt–Sn2 monomers, (Pt–Sn2)2 and (Pt–Sn2)2* dimers in the channels of S-1. All of the intermediates marked with ≠ indicate that they are transition-state intermediates adsorbed on the surfaces of clusters. Projected density of states (PDOS) analysis for C3H8 adsorbed at Pt–Sn2 monomer (n) and (Pt–Sn2)2 dimer (o) confined in the channels of S-1 and (Pt–Sn2)2 dimer with the formation of Pt–Si and Pt–O bonds with framework (p). Blue and red lines represent the spin-up and spin-down electrons of sum PDOS (s-orbitals < −10 eV and p-orbitals > −10 eV) for adsorbed propane at corresponding Pt sites, respectively. Yellow and orange lines represent the spin-up and spin-down electrons of d-orbitals PDOS of corresponding Pt sites, respectively. Notes: the geometries of TSs for the dehydrogenation steps over Pt–Sn2 monomers are schematically represented in panels a–c. From the data, some general trends are observed. (1) In the activated complex, the propane and monovalent group (1-propyl) prefer to be bound to the atop site and the divalent group (propylene) is bonded to the bridge site. The H atom that is detached from the C3 intermediates is relaxed to the atop or bridge site. (2) On the alloyed surfaces, the geometries of TSs are close to FSs on the potential-energy surface.
