M3MoO4(HCO3) (M = Rb, Cs): Cation-tuned synthesis of two noncentrosymmetric molybdate-carbonates with isolated [MoO4] and [HCO3] groups

Abstract

Two molybdate-carbonates M3MoO4(HCO3) (M = Rb, Cs) have been successfully synthesized by cationic tuning. The change in cation size and coordination result in the transformation from cubic space group P4 @#x0305;3m of Na6Li4(MoO4)(CO3)4 to orthorhombic space group Pna21 of M3MoO4(HCO3) (M = Rb, Cs). The Rb/Cs-based polyhedron, isolated [MoO4] and [HCO3] anionic groups are connected by sharing oxygen atoms to form the overall three-dimensional structure. The experimental result shows that they have relatively excellent stability, and wide experimental band gaps of 4.38 and 4.34 eV, respectively. In addition, Rb3MoO4(HCO3) exhibits a good crystal growth habit. Based on this, the crystal of Rb3MoO4(HCO3) with a size of 6 × 2 × 3 mm3 was obtained by the aqueous solution method and its ultraviolet transmission cutoff edge was about 270 nm, which shows that it has a potential application value in the ultraviolet region. The relationship between their structure and performance is analyzed in the first principle.