Synthesis and Crystal Structure of a New Vanadyl Phosphate [H 0.6 (VO) 3 (PO 4 ) 3 (H 2 O) 3 ]·4H 2 O and Its Conversion to Porous Products
Yellow layered VOPO4·2H2O was found to spontaneously, but slowly, convert to a green phase [H0.6(VO)3(PO4)3(H2O) 3]·4H2O upon standing in air. This phase could be prepared hydrothermally from V2O5 + H3PO4 with a small amount of reducing agent added. Single-crystal X-ray analysis gave a = 7.371(3) Å, b = 26.373(11) Å, c = 8.827(4) Å, β = 106.777-(7)°, space group P21/c, and Z = 4. The two vanadyl phosphates are related because the c axis of the green phase is √2·a where a is the a-unit cell dimension of the yellow tetragonal VOPO4·2H2O and the b axis is √2·3a. The green phase was found to intercalate approximately 2 mol of alkylamines/vanadium. A modified gel technique based upon mixtures of amine-intercalated vanadyl phosphate and nickel acetate were utilized to obtain microporous products with nickel polymers. Surface areas as high as 400 m2/g were obtained with pore diameters of 10 to as large as 23 Å. The pore size depended upon the nature of the alcohol solvent, the size of the amine used to enlarge the interlayer space, and the temperature of calcination.
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