Formation of Frustrated Lewis Pairs in Pt_x‐Loaded Zeolite NaY

Abstract

The formation of af rustrated Lewis pair consisting of sodium hydride (Na +

Zeolite-Encaged Isolated Platinum Ions Enable Heterolytic Dihydrogen Activation and Selective Hydrogenations

“…Due to the complex surrounding O sites (Figure S24), a series of O–H stretching frequencies in the range of 3475–3630 cm –1 can be predicted (Table S4), consistent with FTIR observations. This type of dihydrogen heterolysis − resembles the well-known classical Lewis pairs (CLPs), , where the dihydrogen was dissociated by Pt δ+ ···O 2– pairs with direct Pt–O bonding. The activated atomic hydrogen species (H δ− H + ) can be further utilized in selective hydrogenations .…”

“…In situ FTIR spectroscopy was then employed to gain insight into the mechanism of dihydrogen activation. As shown in Figure a, a series of IR bands at 3714, 3668, 3565, 3466, and 3245 cm –1 corresponding to different stretching vibrations of hydroxyls (Table S3) could be observed upon dihydrogen activation on Pt@Y at 373 K, demonstrating the combination of protons with zeolite framework O atoms. − Meanwhile, weak IR bands at 2057 and 1990 cm –1 corresponding to the vibrations of Pt–H species were captured, − which provided strong evidence for the heterolytic dissociation of dihydrogen. In the H–D isotope labeling experiments, IR bands of O–D (2725, 2712, 2665, 2545, and 2402 cm –1 , ν O–H /ν O–D ≈ 1.36) and Pt–D (1455 and 1423 cm –1 , ν Pt–H /ν Pt‑D ≈ 1.40) vibrations were observed (Figure S22).…”

“…As shown in the difference spectrum of dihydrogen activation and the corresponding fitting results (Figure c,d), several 1 H NMR signals could be observed at 5.2, 3.3, 1.5, 1.2, and 0.8 ppm, corresponding to various hydroxyls (Table S5). ,, Unfortunately, the Pt–H signal was not observed by NMR. It should be noted here that the heterolytic dissociation of dihydrogen occurred on both Pt@Y and Pt/Y, while the degree of heterolytic dihydrogen activation showed a huge difference (Figure a).…”

“…The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.1c09535. Experimental materials and details, XRD, Ar sorption isotherms, 29 Si NMR, Py-FTIR, TPD results, SEM and TEM images, catalytic performance tests, and DFT calculations (PDF)…”

“…The as-prepared Pt@Y sample exhibited the typical topological structure of faujasite (Figure S1) with standard type I isotherms (Figures S2 and S3) and appeared as regular crystals with an average size of ∼1.7 μm (Figures S4 and S5). The Si/ Al ratio of Pt@Y zeolite was determined to be 2.7−2.8 by an inductively coupled plasma analysis and a 29 Si nuclear magnetic resonance (NMR) spectrum (Figure S6). A Lewis acid density of 0.133−0.517 mmol g −1 of different strengths was detected with Pt@Y, while no obvious Brønsted acid sites could be detected (Figure S7 and Table S1).…”