Interface Charge Density Matching as Driving Force for New Mesostructured Oxovanadium Phosphates with Hexagonal Structure, [CTA]_xVOPO₄·zH₂O

Abstract

Hexagonal mesostructured mixed-valence oxovanadium phosphates [CTA] x VOPO4·zH2O, in short ICMUV-2, have been synthesized through a S+I- cooperative mechanism using cationic surfactant (cetyltrimethylammonium, CTAB) rodlike micelles as a template. On the lines of the hypothesis that the driving force leading to the formation of mesostructured solids is the charge density matching at the interface between the supramolecular−organic and supramolecular−inorganic moieties, the self-assembling process between CTA+ micelles and VOPO4 q - planar anions can be thought of as consequence of the adequate adjustment of the metal mean oxidation state. X-ray powder diffraction and TEM techniques show that the solids consist of hexagonal arrays of mesopores filled with surfactant, whereas spectroscopic results allow us to propose an oxovanadium phosphate bond topology similar to that observed in the Na x VOPO4·nH2O layered derivatives. The thermal behavior of the mesostructured materials has also been investigated, given that both the easy elimination of CTA+ species and their V:P = 1:1 molar ratio make ICMUV-2 solids adequate pyrolytic precursors of the (VO)2P2O7 catalyst.

Insertion study of alkali metal cations into layered vanadium oxide foam

“…The original spectrum (Fig. 1a) showed sharp peaks around 2920, 2850, 1480 and 1400 cm -1 that could be assigned to c as (C-H), c s (C-H), d(CH 2 ), and c(C-C) vibration modes of CH 3 (CH 2 ) 15 NH 2 [22,23]. The bands at 3490 and 3090 cm -1 are assigned to the N-H stretching vibration modes and the band at 1610 cm -1 assigned to the N-H bending vibration mode of the hexadecylamine [24].…”

Partial Oxidation of Isobutane over Vanadium Phosphorus Oxides

“…It is obvious that the product NV0 synthesized from a mixture of reactants without DA shows no diffraction peak in the 2h Partial Oxidation of Isobutane 357 region of 1.2-10.0°in the XRD pattern, but yields many peaks at 10-40°(not shown here). However, VPO catalyst prepared by using DA (e.g., N/V = 1/2) shows two reflections at 3.5°and 6.9°corresponding to the (0 0 1) and (0 0 2) reflections, indicating that a lamellar VPO mesophase is obtained [7,10,16]. Therefore, it is apparent that the existence of DA is essential to the formation of VPO having the mesoporous structure.…”

“…In the past years, there have been many reports about the synthesis of mesostructured vanadium phosphate (VPO) phases by using cationic (alkyl trimethyl ammonium salts), anionic (alkyl sulfonates and phosphates) and primary alkylamines as structure directing surfactants [7][8][9][10][11][12][13][14][15][16][17]. However, these materials are mainly applied in relatively low temperature reaction because the surfactant is inevitably lost at relatively high temperature.…”

Ordered Meso‐ and Macroporous Binary and Mixed Metal Oxides

“…Amoros et al [116] have described the synthesis of hexagonal mesostructured oxovanadium phosphates, denoted as ICMUV-2. However, the removal of surfactant from their vanadium phosphates resulted in the collapse of the mesostructure.…”