Exploring Oxonitridosilicate Synthesis: From Oxide Zeolites to Nitride Frameworks

In this study, we synthesized the first CAN (<b><i>can</i></b>crinite)-typed zeolite-like oxonitridosilicates, <i>Ln</i>₅Ca₉O₂(SiNO₃)[Si₁₂N₂₄] (<i>Ln</i> = La and Ce). The crystal structure of La₅Ca₉O₂(SiNO₃)[Si₁₂N₂₄] was determined through single-crystal X-ray diffraction (SCXRD) data and neutron powder diffraction (NPD) data refinement. The compound crystallizes in hexagonal space group <i>P</i>6₃<i>mc</i> (No. 186) with <i>a</i> = 12.9875(2) Å, <i>c</i> = 5.2072(1) Å, and <i>Z</i> = 1. The anionic framework of La₅Ca₉O₂(SiNO₃)[Si₁₂N₂₄] is entirely constructed from [SiN₄] tetrahedra, forming larger-sized composite building units, <i>t-can</i> and <i>t-ato</i>. The Ca²⁺ cations in the <i>t-can</i> cage contribute to balancing the charge difference originating from N^3- substitution for O^2- in La₅Ca₉O₂(SiNO₃)[Si₁₂N₂₄], which was revealed by the charge density difference calculation. The Ce³⁺-doped La₅Ca₉O₂(SiNO₃)[Si₁₂N₂₄] shows a broad-band orange-red emission peaking at λ = 630 nm under UV light excitation.