A series of novel phosphites/phosphates with deep-ultraviolet cut-off edges from 0D polar to 3D non-polar architectures

Abstract

Four new phosphites/phosphates, namely Al[P₂O₃(OH)₃](H₂O), Al[(HPO₃)(OH)(H₂O)], Ca[HPO₃] and Al₃P₆O_19.5, were designed and synthesized by low temperature flux methods. They crystallized in P6₃mc, P, P4₃2₁2, and P6₃/m space groups, respectively. The basic units of Al[P₂O₃(OH)₃](H₂O), Al[(HPO₃)(OH)(H₂O)] and Ca[HPO₃] are composed of [PO₃]³⁻ or/and [AlO₆]⁹⁻ groups, whereas the structure of Al₃P₆O_19.5 is built from [PO₄]³⁻ tetrahedra and [AlO₆]⁹⁻ octahedra. The structure of Al[P₂O₃(OH)₃](H₂O) features a two-dimensional (2D) layered motif of Al[P₂O₃(OH)₃]. Meanwhile, Al[(HPO₃)(OH)(H₂O)] has high porosity and relatively large channels, and has an excellent molecular sieve structure. Both Al[P₂O₃(OH)₃](H₂O) and Al[(HPO₃)(OH)(H₂O)] display deep ultraviolet (UV) cut-off edges of ∼195 nm and ∼193 nm. The three-dimensional (3D) structure of Al₃P₆O_19.5 is formed by [Al₂O₉] dimers connected with six PO₄ tetrahedra, and one PO₄ tetrahedron linked three [Al₂O₉] dimers alternately. Importantly, Ca[HPO₃] shows a moderate second harmonic generation (SHG) effect with a short UV cut-off edge of ∼192 nm in the deep-UV region. The syntheses and topological structures of Al[P₂O₃(OH)₃](H₂O), Al[(HPO₃)(OH)(H₂O)], Ca[HPO₃] and Al₃P₆O_19.5, together with some related properties, such as nonlinear optical (NLO) properties, elemental analysis, thermal stability, infrared spectroscopy, Raman spectroscopy and UV-vis diffuse reflectance spectroscopy, are also discussed.