Transition metal tetramolybdate dihydrates MMo4O13·2H2O (M=Co,Ni) having a novel pillared layer structure

Abstract

a b s t r a c tHydrothermal synthesis in the M/Mo/O (M ¼ Co,Ni) system was investigated. Novel transition metal tetramolybdate dihydrates MMo 4 O 13 Á 2H 2 O (M ¼ Co,Ni), having an interesting pillared layer structure, were found. The molybdates crystallize in the triclinic system with space group PÀ1, Z ¼ 1 with unit cell (6)1 for NiMo 4 O 13 Á 2H 2 O The structure is composed of two-dimensional molybdenum-oxide (2D Mo-O) sheets pillared with CoO 6 octahedra. The 2D Mo-O sheet is made up of infinite straight ribbons built up by corner-sharing of four molybdenum octahedra (two MoO 6 and two MoO 5 OH 2 ) sharing edges. These infinite ribbons are similar to the straight ones in triclinic-K 2 Mo 4 O 13 having 1D chain structure, but are linked one after another by corner-sharing to form a 2D sheet structure, like the twisted ribbons in BaMo 4 O 13 Á 2H 2 O (or in orthorhombic-K 2 Mo 4 O 13 ) are.

Theoretical and Experimental Study of Structural Phases in CoMoO4†

“…Furthermore, one might consider a possible relationship to the experimentally observed hydrated Co 2 Mo 3 O 8 x H 2 0 structure. [39] In addition, we show CoMoO 4 -PRD8, another structure candidate related to the CoMoO 4 (II) modification (see Figure 4a), although this modification only shows triclinic symmetry with space group P-1 (no. 2).…”

Synthesis and crystal structure of layered molybdate NH4Co2OH(MoO4)2⋅H2O

“…However, for these phases, no structural data were reported. The known structures of cobalt molybdate phases consist of cobalt atoms coordinated octahedrally with oxygen to form octahedra (Eda et al, 2005(Eda et al, , 2009.…”

“…There are three known polymorphic forms of cobalt molybdate CoMoO 4 : the pale green low-temperature α phase (monoclinic, space group C 2/ m ) (Smith and Ibers, 1965), the black high-pressure hp phase (monoclinic, space group P 2/ c ) (Livage et al, 2002) and the pale violet high-temperature β phase (monoclinic, space group C 2/ m ) (Courtine et al, 1968). The hydrate phases CoMoO 4 ⋅3/4H 2 O (triclinic, space group P- 1) and CoMo 4 O 13 ⋅2H 2 O (triclinic, space group P- 1) are also known (Eda et al, 2005, 2009). Additionally, two more hydrates were identified in the literature: CoMoO 4 ⋅0.9H 2 O (PDF 00-014-0086) and CoMoO 4 ⋅1.3H 2 O (PDF 00-014-0087) (Liu et al, 2012; Kim et al, 2019).…”

“…The known structures of cobalt molybdate phases consist of cobalt atoms coordinated octahedrally with oxygen to form octahedra [CoO 6 ]. In the β-phases and CoMoO 4 ⋅3/4H 2 O hydrate, molybdenum is present in tetrahedra [MoO 4 ], and in the α-, hp-phases, and CoMo 4 O 13 ⋅2H 2 O hydrate in octahedra [MoO 6 ] (Eda et al, 2005, 2009).…”