Functional layered materials with heavy metal lone pair cations, Pb2+, Bi3+, and Te4+

Abstract

Owing to their various important structure-driven properties, functional layered materials have been of great interest. In this feature article, a series of recently discovered novel layered materials with heavy metal lone pair cations containing Pb²⁺, Bi³⁺, and Te⁴⁺ are introduced. The layered materials include (1) the first Pb²⁺-Kemp's triacid coordination complex showing selective CO₂ adsorption and an intercalative ligand addition reaction, Pb₃[C₆(CH₃)₃(CO₂)₃H₆]₂[DMF]₃, (2) a tailor-made polar lead borate chloride with a very strong second-harmonic generation (SHG) response, Pb₂BO₃Cl, (3) a white light emitting single component Pb⁺-based coordination polymer exhibiting high quantum efficiency and thermal stability, Pb[NC₅H₃(CO₂)₂], (4) noncentrosymmetric (NCS) n = 3 Dion–Jacobson layered perovskites with a variety of NCS characteristics, polar RbBi₂Ti₂NbO₁₀ and nonpolar CsBi₂Ti₂TaO₁₀, (5) layered bismuth oxyfluoride nitrates revealing photocatalytic properties and large SHG, Bi₂OF₃(NO₃) and Bi₆O₆F₅(NO₃), (6) a layered bismuth tellurium nitrate hydroxide with multiple NCS chromophores, Bi₂Te₂O₆(NO₃)₂(OH)₂(H₂O), (7) a mixed-valent layered tellurite–tellurate with robust ion-exchange behavior, Na₂Te₂O₆·1.5H₂O, and (8) a metastable lithium molybdenum tellurite undergoing Li⁺-exchange-driven facile structural transformation reactions, Li₂Mo₃TeO₁₂. The syntheses, structures, representative properties, and structure–property relationships for the layered materials are presented.