Synthesis, characterization and properties of microporous lanthanide silicates: K8Ln3Si12O32NO3·H2O (Ln = Eu, Tb, Gd, Sm)

A family of microporous lanthanide silicates, K8Ln3Si12O32NO3·H2O (denoted LnSiO-CJ3, Ln = Eu, Tb, Gd, Sm), was synthesized under mild hydrothermal conditions at 503 K. The X-ray powder diffraction patterns of these compounds reveal that they are isostructural. The structure of EuSiO-CJ3 was determined by single-crystal X-ray diffraction analysis. It crystallizes in triclinic space group P-1 (No. 2) with a = 11.599(2) Å, b = 12.225(2) Å, c = 13.829(3) Å, α = 112.99(3)°, β = 92.05(3)°, γ = 90.57(3)°. The structure is based on [Si3O8]n4n− layers with 6-, 8-, 12-rings that are connected by EuO6 octahedra to form a 3-D framework with 8-ring channels along the [001] direction. Charge neutrality is achieved by the K+ and NO3− ions located in the channels. The framework of EuSiO-CJ3 shows good thermal stability, which can be stable up to 1273 K. Ion-exchange capacity of EuSiO-CJ3 was investigated by the exchange of NO3− ions with halide ions (F−, Cl−, Br−). The peaks in the emission spectra of LnSiO-CJ3 (Ln = Eu, Tb) belong to the characteristic transitions of Ln3+ (Ln = Eu, Tb) respectively. The lifetime measurements of LnSiO-CJ3 (Ln = Eu, Tb) suggest the presence of three Ln3+ (Ln = Eu, Tb) environments, which are consistent with the crystallographic results.

A family of microporous lanthanide silicates: K8Ln3Si12O32NO3·H2O (Ln = Eu, Tb, Gd, Sm) was prepared under mild hydrothermal conditions at 503 K. Their structures are isostructural, consisting of [Si3O8]n4n− layers connected by EuO6 octahedra to form a 3-D framework with 8-ring channels along the [001] direction. The K+ and NO3−-ions are located in the void space. The compounds show good thermal stability, ion-exchange capacity and photoluminescent properties. Figure optionsDownload as PowerPoint slide