Mesoporous Molybdenum–Tungsten Mixed Metal Oxide: A Solid Acid Catalyst for Green, Highly Efficient sp³–sp² C–C Coupling Reactions

Abstract

A mesoporous molybdenum tungsten mixed metal oxide with high surface area (173 m2/g) was synthesized by using metal dissolution coupled with a surfactant assisted reverse micelle formation synthesis method. Comprehensive characterization of the mixed oxide was performed by using PXRD, Raman, BET, SEM, EDX, TEM, and XPS. Thus, the formation of α-Mo0.5W0.5O3 with a homogeneous distribution of Mo and W throughout the material was seen. Furthermore, multiple oxidation states of molybdenum (Mo6+ and Mo5+) and a single oxidation state of tungsten (W6+) were observed. The weak/moderate acidic sites present in the mixed metal oxide resulted in excellent catalytic properties toward the sp3–sp2 carbon–carbon coupling reactions. The coupling of benzyl alcohol and toluene was completed within 15 min at 110 °C with 99% yield.

Mesoporous Crystalline Niobium Oxide with a High Surface Area: A Solid Acid Catalyst for Alkyne Hydration

“…Strong and weak/moderate acid site densities were calculated using a neutralization ion-exchange method as reported in the literature . To calculate strong acid site density, 50 mg of the catalyst was mixed with 100 mL of 1.0 M NaCl and stirred overnight.…”

“…Strong and weak/moderate acid site densities were calculated using a neutralization ion-exchange method as reported in the literature. 4 To calculate strong acid site density, 50 mg of the catalyst was mixed with 100 mL of 1.0 M NaCl and stirred overnight. The obtained solution was filtered, and a 25 mL aliquot of this solution was titrated with 0.01 M NaOH in the presence of phenolphthalein indicator.…”

“…The synthesis of mesoporous materials with a transition-metal oxide framework has been extensively studied over the past decade. So far, several oxides including TiO 2 , WO 3 , MoO 3 , CeO 2 , and Mn 2 O 3 have been widely used because of their potential applications in many advanced areas. − Recently, niobium oxide has gained increasing attention as a multifunctional material due to its unique chemical, physical, optical, and electronic properties such as the stability in aqueous media, water-tolerant surface acidity, wide band gap, photoelectric, and photocatalytic properties. − Studies have shown that these properties make Nb 2 O 5 a promising material in the fields of catalysis, sensors, photocatalysis, and electrochemistry. − …”

Recent advances in non-noble metal-based oxide materials as heterogeneous catalysts for C–H activation

“…These works reveal the importance of surface acidity, which can be induced in metal oxides via surface engineering, to initiate the classic C-C coupling reaction, with potential to avoid the use of harsh acid catalysts. 48 The other versatile reactions in the C-C coupling space are the Sonogashira and Heck reactions. It was a significant breakthrough in organic chemistry to directly form CvC and C-C bonds in a single step to synthesize numerous complex compounds, which have been actively used in the agrochemical, fine chemical, and pharmaceutical industries.…”

“…These works reveal the importance of surface acidity, which can be induced in metal oxides via surface engineering, to initiate the classic C–C coupling reaction, with potential to avoid the use of harsh acid catalysts. 48…”