Isomorphous substitution of transition-metal ions in the nanoporous nickel phosphate VSB-5.
The transition-metal-incorporated nickel phosphate molecular sieves (TMI-VSB-5) have been hydrothermally synthesized at 453 K in weak basic conditions under microwave irradiation. By means of X-ray diffraction, inductively coupled plasma (ICP), ultraviolet-visible (UV-vis) diffuse reflectance, and Mössbauer spectroscopies, successful isomorphous (at least partial) substitution of transition-metal ions in the VSB-5 framework has been verified. Characterization results show that the framework structure of nanoporous VSB-5 can accommodate a substantial level of isomorphous substitution of transition-metal ions up to about 10, 5, and 3 atom % for Fe, Mn, and V, respectively, in both octahedral nickel sites (Mn and Fe) and tetrahedral phosphorus sites (V). The isomorphous substitution including the replacement mechanism was studied by not only the change of unit cell parameters but also spectroscopic analysis. The unit cell parameters of TMI-VSB-5 including a unit cell volume and a-axis length relied on the ionic radii difference between the incorporated ion and the original framework ions such as Ni or P (RTMI - RNi or RTMI - RP).
Jhung
Sung Hwa
SH
Research Center for Nanocatalysts, Korea Research Institute of Chemical Technology, P.O. Box 107, Yusung, Daejeon 305-600, Korea.
Chang
Jong-San
JS
Hwang
Young Kyu
YK
Grenèche
Jean-Marc
JM
Férey
Gérard
G
Cheetham
Anthony K
AK