New RE microporous heteropolyhedral silicates containing 4(1)5(1)6(1)8(2) tetrahedral sheets

Area of Science:

• Materials Science
• Inorganic Chemistry
• Crystallography

Background:

• Microporous materials are crucial for various applications, including catalysis and separation.
• Heteropolyhedral silicates offer unique structural diversity and potential for novel properties.
• Understanding the structure-property relationships in these materials is essential for targeted design.

Purpose of the Study:

• To hydrothermally synthesize and structurally characterize novel heteropolyhedral microporous silicates.
• To investigate the framework topology and channel systems within these new silicate structures.
• To explore the role of rare-earth elements and charge-balancing cations in framework formation.

Main Methods:

• Hydrothermal synthesis in Teflon-lined autoclaves at 503 K.
• Single-crystal X-ray diffraction for structural determination.
• Analysis of diffraction data, including merohedral twinning for some samples.

Main Results:

• Four isotypic heteropolyhedral microporous silicates, A(3)RESi(6)O(15).2.25H(2)O, were successfully synthesized.
• The structures are based on corrugated 4(1)5(1)6(1)8(2) silicate sheets interconnected by seven-coordinated rare-earth (RE) polyhedra.
• A microporous framework with three systems of ellipsoidal channels (largest effective width 4.7 x 2 Å) was formed, hosting water molecules and alkaline ions.

Conclusions:

• The study presents a new family of microporous silicate structures with a unique framework topology.
• The interconnected silicate sheets and RE polyhedra create a robust framework with accessible channels.
• The findings contribute to the understanding of structure formation in rare-earth-containing microporous silicates.