Targeted synthesis of a polypyridyl polyoxometalate coordination complex using microwave-assisted reaction conditions

Incorporation of Keggin-based H3PW7Mo5O40 into bentonite: synthesis, characterization and catalytic applications

The Keggin-based molybdo-substituted tungstophosphoric acid, H3[PW7Mo5O40]·12H2O, were synthesized and incorporated with a bentonite clay by using a wetness impregnation method. The catalysts were characterized using several methods, such as inductively coupled plasma-atomic emission spectroscopy (ICP-AES), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), and thermogravimetric and differential thermal analysis (TG-DTA). This extremely active catalytic system provides a green strategy for the synthesis of 1,8-dioxo-octahydroxanthene and 1,8-dioxo-decahydroacridine derivatives under solvent free conditions at 80 °C with a good reaction mass efficiency, effective mass yield, and excellent atom economy. Both the surface acidity and catalytic activity sharply increased after H3[PW7Mo5O40]·12H2O was impregnated with bentonite clay. In addition, the PW7Mo5/bentonite catalyst can be conveniently recovered and reused numerous times without demonstrating a significant loss in activity.

Tungsten-substituted molybdophosphoric acid impregnated with kaolin: effective catalysts for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones via biginelli reaction

A series of highly reusable heterogeneous catalysts (10-25 wt% PMo7W5/kaolin), consisting of tungsten-substituted molybdophosphoric acid, H3PMo7W5O40·24H2O (PMo7W5) impregnated with acid treated kaolin clay was synthesized by the wetness impregnation method. The newly synthesized catalyst was fully characterized using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), Fourier transform infrared (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis and thermal analysis (TG-DTA). The synthesized materials were shown to be efficient in the synthesis of 3,4-dihydropyrimidin-2(1H)-ones via Biginelli reaction under solvent-free conditions. The obtained results indicate that 20% PMo7W5/kaolin catalyst showed remarkably enhanced catalytic activity compared to the bulk PMo7W5 catalyst, and also the (10 and 15%) PMo7W5 catalyst supported on kaolin clay.