Unraveling a Biomass-Derived Multiphase Catalyst for the Dehydrogenative Coupling of Silanes with Alcohols under Aerobic Conditions

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acssuschemeng.0c08953. [EN] Herein, a novel silver and chromium nanostructured N-doped carbonaceous material has been synthesized by a biomass-annealing approach using readily available chitosan as a raw material. The resulting catalyst AgCr@CN-800 has been applied for the dehydrogenative coupling reaction of various silanes with different alcohols to obtain the corresponding silyl ethers under aerobic and mild conditions. Besides excellent activity and selectivity, the as-prepared catalyst exhibits good stability and reusability. Characterization by X-ray diffraction, X-ray photo-electron spectroscopy, inductively coupled plasma mass spectrometry, and high-resolution transmission electron microscopy (TEM) in combination with careful examination of the structure with Cs-corrected high-angle annular dark-field scanning TEM revealed that the catalyst AgCr@CN-800 comprises Ag- and CrN-aggregated particles, as well as highly dispersed Ag-N-x and Cr-N-x sites embedded in N-doped graphitic structures. A comparative catalytic study using structure-related catalysts in combination with acid-leaching treatments has shown that the most active species are the Ag particles and that their activity is boosted by the presence of Cr-derived species. By in situ Raman spectroscopy experiments, it has been found that the dehydrogenative coupling of silanes with alcohols in the presence of catalyst AgCr@CN-800 takes place through an oxygen-assisted mechanism. The authors thank the financial support from MICIU/AEI/FEDER (PGC2018-094417-B-I00 and RTI2018-098237-B-C22) and Universitat Jaume I (UJI-A2019-16, UJI-B2019-30, and UJI-B2018-23). I.S. thanks the Spanish Ministerio de Economia, Industria y Competitividad (MINECO) for a postdoctoral "Juan de la Cierva-Incorporacion" fellowship (IJCI-2016-30590), and the financial support from the "Jose Castillejo" Mobility Program (CAS19/00339) of the Ministerio de Ciencia, Innovacion y Universidades (MICIU). S.M. acknowledges DGA/fondos FEDER (construyendo Europa desde Aragon) for funding the research group Platon (E31_17R). D.V.-E. thanks the MICIU for a FPU grant (FPU15/03011). E.L. and M.A. thank the financial support from FAPES