Thin-Layered Sheets of VOHPO4·0.5H2O Prepared from VOPO4·2H2O by Intercalation−Exfoliation−Reduction in Alcohol

Intercalation of alcohol into layers of VOPO4·2H2O crystallites, exfoliation using alcohol (containing three to five carbon atoms) into delaminated sheets, and subsequent reduction by reflux in alcohol into thin-layered VOHPO4·0.5H2O were investigated using XRD, IR, SEM, determination of the absorption of alcohol, elemental analysis, and TG/DTA. Stepwise thermal treatment of an alcohol suspension of VOPO4·2H2O crystallites, initially having shapes of large square platelets (length of about 20 μm and thickness of about 1 μm), resulted in the corresponding homogeneous solutions. XRD, IR, and SEM data were used to explain the intercalation of alcohol and exfoliation in forming the solutions containing the delaminated sheets. The exfoliated sheets were reconstructed as thin-layered VOPO4·2H2O with small flakelike shapes by the removal of the alcohol. Refluxing the VOPO4·2H2O solution of 1-propanol or 1-butanol yielded flower-petal-like crystallites (length of about 5 μm and thickness of about 0.1 μm) of the corresponding vanadyl alkyl phosphates VO[(OH)1 - x (OR) x ]PO3· (H2O) y (ROH) z (R = alkyl group). In contrast, refluxing a solution of secondary alcohol such as 2-butanol yielded fragment-like crystallites (length of about 1 μm and thickness of about 0.1 μm) of the pure VOHPO4·0.5H2O phase. These results demonstrated that the processes of intercalation, exfoliation, and reduction in alcohol are critical in the final microstructure of the vanadium(IV) phosphate compounds.