Exploring Oxonitridosilicate Synthesis: From Oxide Zeolites to Nitride Frameworks

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 N3– substitution for O2– 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.