Issue 10, 2020

Development of magnesium oxide–silver hybrid nanocatalysts for synergistic carbon dioxide activation to afford esters and heterocycles at ambient pressure

Abstract

Multi-metallic hybrid nanocatalysts consisting of a porous metal oxide host and metal satellite guests serve as a scaffold for multi-step transformations of divergent and energy-challenging substrates. Here we have developed a 3D porous MgO framework (Lewis basic host) with Ag0 nanoparticles (noble metal guest) for ambient pressure activation and insertion of CO2 into unsaturated alkyne substrates. The hybrid MgO@Ag-x (x = 2, 5, 7, 8 at% Ag) catalysts are synthesized by impregnating Ag+ ions in porous MgO cubes followed by reduction using NaBH4. Morphological (SEM, TEM, EDX mapping) and structural (PXRD, XPS) characterization reveal that the micron-sized hybrid cubes derive from self-assembly of ∼100 nm (edge length) MgO cubes decorated with ∼5 to 25 nm Ag0 NPs. Detailed XPS analysis illustrates Ag0 is present in two forms, <10 nm NPs and ∼25 nm aggregates. The MgO@Ag-7 catalyst is effective for inserting CO2 into aryl alkynes followed by SN2 coupling with allylic chlorides to afford a wide range of ester and lactone heterocycles in excellent yields (61–93%) and with low E-factor (2.8). The proposed mechanism suggests a CO2 capture and substrate assembly role for 3D porous MgO while Ag0 performs the key activation of alkyne and CO2 insertion steps. The catalyst is recyclable (5×) with no significant loss of product yield. Overall, these results demonstrate viable approaches to hybrid catalyst development for challenging conversions such as CO2 utilization in a green and sustainable manner.

Graphical abstract: Development of magnesium oxide–silver hybrid nanocatalysts for synergistic carbon dioxide activation to afford esters and heterocycles at ambient pressure

Supplementary files

Article information

Article type
Paper
Submitted
25 Nov 2019
Accepted
23 Mar 2020
First published
24 Mar 2020

Green Chem., 2020,22, 3170-3177

Author version available

Development of magnesium oxide–silver hybrid nanocatalysts for synergistic carbon dioxide activation to afford esters and heterocycles at ambient pressure

U. Gulati, U. Chinna Rajesh, D. S. Rawat and J. M. Zaleski, Green Chem., 2020, 22, 3170 DOI: 10.1039/C9GC04040D

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements