Synthesis and characterization of nanoporous nickel phosphates VSB-1 with systematic doping of cobalts in the frameworks

Systematic doping of cobalts in the VSB-1 frameworks has been carried out under hydrothermal condition. Large amount of cobalts doped or bimetal Co and Ni VSB-1 have been successfully synthesized. The coordinated environment, amount and valence of cobalt ions in the frameworks of VSB-1 have been characterized by various techniques. The amount of cobalts doped in CoVSB-1 is up to 52.0mol.% relative to that of Ni in the pure VSB-1, which is very unusual and much higher than the highest degree of substitution of cobalts for Al³⁺ in CoAPO-50 (37.5mol.%). The higher values of BET surface areas for CoVSB-1 (164 and 156m²/g for samples 3 and 5, respectively) than that of VSB-1 (134 m²/g) and the similar type I nitrogen adsorption isotherm curves show that the nanoporous CoVSB-1 should be more open without cobalts in the channels. The increase of unit cells in the size and Co²⁺ polyhedra absorption bands of UV-vis spectra reveal that cobalt ions substitute predominantly for six-coordinated nickel species in the frameworks of Co VSB-1.