DFT-assisted structure determination of α1- and α2-VOPO4: new insights into the understanding of the catalytic performances of vanadium phosphates

Abstract

Structural investigations on vanadium phosphates, which are extensively used as catalysts in industry, often resulted in important advances in the understanding of the mechanisms driving the catalytic oxidation of light hydrocarbons. Layer translations in the two lamellar vanadium phosphates α₁- and α₂-VOPO₄ phases identified during the catalysis were investigated by the combination of first-principles calculations, synchrotron X-ray powder diffraction, single-crystal X-ray diffraction and solid-state NMR. This analysis reveals an important feature: the α₁-form is the only polymorph of VOPO₄ to exhibit layer translations that prevent the formation of infinite VO₆ chains. A detailed investigation of this structural characteristic in vanadium phosphates reveals the correlation between the presence of infinite VO₆ chains and the catalytic performances of related phases.