A new good thermal stability hybrid material based on heptamolybdate cluster: Synthesis and structural characterization

Abstract A new microporous polyoxomolybdate, (C4H7N2)9(NH4)3[Mo7O24]2•4H2O ([C4H7N2]+ = 2-methylimidazolium), was prepared at room temperature by reacting ammonium heptamolybdate tetrahydrate and 2-methylimidazole in a 1:4 molar ratio in water and characterized by infrared, TGA-DTA analysis and single-crystal X-ray diffraction. The compound is a heptamolybdate anion which crystallizes as a mixed salt of both ammonium [NH4]+ and 2-methylimidazolium [C4H7N2]+. The crystal structure of the compound is composed of [Mo7O24]6– clusters connected in a tridimensional network by [C4H7N2]+ and [NH4]+ cations and water molecules via hydrogen-bonding interactions. The relatively high thermal stability may be due to the existence of the network of hydrogen bonds and electrostatic interactions. Obtaining of compound from (NH4)6[Mo7O24]•4H2O shows that the transition from one polyoxomolybdate to another is possible through substitution reactions at room temperature, despite their stability. This material obtained could be used as catalyst and catalyst support.