Exploring Oxonitridosilicate Synthesis: From Oxide Zeolites to Nitride Frameworks

Abstract

In this study, we synthesized the first CAN (cancrinite)-typed zeolite-like oxonitridosilicates, Ln₅Ca₉O₂(SiNO₃)[Si₁₂N₂₄] (Ln = 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 P6₃mc (No. 186) with a = 12.9875(2) Å, c = 5.2072(1) Å, and Z = 1. The anionic framework of La₅Ca₉O₂(SiNO₃)[Si₁₂N₂₄] is entirely constructed from [SiN₄] tetrahedra, forming larger-sized composite building units, t-can and t-ato. The Ca²⁺ cations in the t-can 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.