Designing Synergistic Nanocatalysts for Multiple Substrate Activation: Interlattice Ag–Fe3O4 Hybrid Materials for CO2‑Inserted Lactones

• Published in: ACS catalysis Vol. 10; no. 5; pp. 3349 - 3359
• Main Authors: Rajesh, U. Chinna, Losovyj, Yaroslav, Chen, Chun-Hsing, Zaleski, Jeffrey M
• Format: Journal Article
• Language: English
• Published: American Chemical Society 06-03-2020
• Subjects: interlattice metal oxide catalysis; alkyne bond activation; complementary nanocatalysts; tandem reaction nanocatalysis; lactone heterocycles; CO2 insertion
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.9b04260

Multimetallic architectures that combine chemically diverse materials to affect tandem reactions within a single scaffold drive future nanocatalyst development. Here, we show the unique, interlattice growth of the small molecule activating Ag0 guest within the Lewis acidic/basic Fe3O4 octahedral host (Fe3O4@Ag-40, 10, 6, 2 at %) via a polyol-hydrothermal procedure. Microscopic (scanning electron microscopy and energy-dispersive X-ray spectroscopy ) and structural characterization (powder X-ray diffraction and X-ray photoelectron spectroscopy) of the Fe3O4@Ag hybrid materials reveal doping of Ag0 in O h Fe2+ substitutional vacancies of the Fe3O4 host and Ag0 nanoparticle growth on and embedded deep within (>400 nm, Ar+ sputtering) the octahedra. These hybrid materials activate CO2 and perform C­(sp)–H and C­(sp3)–Cl bond scission of alkyne substrates to selectively produce lactone heterocycles in up to 85% yield. Control reactions delineate two distinct pathways for the mechanism involving the complementarity of interfacial sites where alkyne activation occurs at Fe–O sites and CO2 incorporation is predominately managed by Ag0. The recyclability of the Fe3O4@Ag-40B hybrid catalyst is demonstrated over five cycles and it shows the structural integrity of the octahedra, but a gradual drop in yield of the product from 85 to 45% due to slow depletion of surface Ag NPs is observed. Together, these results illustrate a rare understanding of the cooperative synergy and mechanism of multimetallic nanocatalyst interfaces for multiple substrate reactivity.