Design and characterization of an urea-bridged PMO supporting Cu(II) nanoparticles as highly efficient heterogeneous catalyst for synthesis of tetrazole derivatives

Abstract

In this work, a new periodic mesoporous organosilica with urea-bridges produced by the reaction of (3-aminopropyl)triethoxysilane and toluene-2,4-diisocyanate (APS-TDU-PMO) is introduced. The obtained APS-TDU-PMO was found to be an appropriate support for loading of Cu(II) nanoparticles to afford supramolecular Cu@APS-TDU-PMO nanocomposite. Uniformity and mesoporosity of both synthesized nanomaterials including APS-TDU-PMO and Cu@APS-TDU-PMO were proved by different spectroscopic, microscopic or analytical techniques including FTIR, EDX, XRD, FESEM, TEM, BET, TGA and DTA. Furthermore, the prepared Cu@APS-TDU-PMO nanomaterial was also used, as a heterogeneous and recyclable catalyst, for the synthesis of tetrazole derivatives through cascade condensation, concerted cycloaddition and tautomerization reactions. Indeed, the main advantages of this Cu@APS-TDU-PMO is its simple preparation and high catalytic activity as well as proper surface area which enable it to work under solvent-free conditions. Also, the introduced Cu@APS-TDU-PMO heterogeneous catalyst showed good stability and reusability for six consecutive runs to address more green chemistry principles.

Figure 1

Schematic structure of the Cu@APS-TDU-PMO nanoreactor (1) for the three-component condensation of aldehydes (2a–i), malononitrile (3), and sodium azide (4).

Figure 2

FTIR spectra of the APS-TDU-PMO (a) and Cu@APS-TDU-PMO (1, b).

Figure 3

TGA and DTA curves of the Cu@APS-TDU-PMO nanomaterial (1).

Figure 4

FESEM (a–c) and TEM images (d–f) of the Cu@APS-TDU-PMO nanoreactor (1).

Figure 5

Low-angle (a) and wide angle (b) XRD patterns of the APS-TDU-PMO; Wide angle XRD pattern of the Cu@APS-TDU-PMO (1, c).

Figure 6

EDX analysis of the Cu@APS-TDU-PMO nanocomposite (1).

Figure 7

N₂ adsorption–desorption isotherm of the Cu@APS-TDU-PMO mesoporous material (1).

Figure 8

The proposed mechanism for the synthesis of 2-(1H-tetrazol-5-yl) acrylonitrile derivatives in the presence of Cu@APS-TDU-PMO nanoreactor (1).

Figure 9

Reusability of the heterogeneous Cu@APS-TDU-PMO catalyst (1) for the synthesis of 5a.

Figure 10

FTIR spectra and low angle XRD pattern of the reused Cu@APS-TDU-PMO catalyst (1) after six consecutive runs.

Figure 11

General procedure for the preparation of Cu@APS-TDU-PMO nanocatalyst (1).