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