Synthesis and crystal structure of a new vanadyl phosphate [H-0.6(VO)(3)(PO4)(3)(H2O)(3)]center dot 4H(2)O and its conversion to porous products
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Yellow layered VOPO42H2O 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) , b = 26.373(11) , c = 8.827(4) , = 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 2a where a is the a-unit cell dimension of the yellow tetragonal VOPO42H2O and the b axis is 23a. 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 . 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.