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An exploratory study of the lead-tellurium-oxygen phase space led to two new compounds, Ba3PbTe6O16 (BPTO) and Na2Pb9(μ6-O)2(Te2O10)2 (NPTO), which were synthesized under hydrothermal conditions at 550 °C and 210 °C, respectively, and characterized by single-crystal X-ray diffraction, infrared and X-ray photoelectron spectroscopy. BPTO adopts a layer structure. The Te4+ cation in BPTO is bonded to four oxygen atoms at about 2.0 A with two more oxygens at about 3.0 A. The seesaw-shaped TeO4 units share corners to form 2D layers containing six-membered rings and the Ba2+ and Pb2+ cations are situated in the interlayer region. The structure of NPTO contains dimers of edge-sharing Te6+O6 octahedra, which are connected through five-coordinate Pb2+ cations. A unique six-coordinate O atom is at the center of the octahedron formed by five Pb2+ and one Na+ cations. BPTO is one of the few metal tellurites which were synthesized under supercritical hydrothermal reaction conditions. The Pb2+ cation in NPTO shows pronounced stereochemical effects of the lone electron pair. In contrast, BPTO shows no stereochemical evidence of the inert pair.

The design and synthesis of crystalline materials have been a subject of intensive research because of their interesting structures, physicochemical properties, and potential applications. However, the crystalline structure of organic-inorganic hybrid materials collapses to lose the structural features of the original networks and/or frameworks when exposed to different stimuli such as pH, vapor, water, high temperature, and organic solvents. This hampers further studies focusing on practical applications. Although several review articles provide reasonable pathways for the preparation of stable metal-organic frameworks (MOFs) and coordination polymers (CPs), the synthesis and design of stable materials containing organic species remain challenging. In this frontier article, we discuss the development of crystalline MOF, CP, metallophosphate, and metallophosphite materials, and provide a feasible approach for the formation of stable organic-inorganic hybrid compounds that combine MOFs (or CPs) and phosphate (or phosphite) building elements. In addition to their interesting structures, the synthetic strategies and structural stabilities of such hybrid composites are also presented.

The first example of a thio-functionalized zincophosphite material (NTOU-2S) incorporating the 2,5-thiophenedicarboxylate (TPDC) ligands was synthesized using a hydro(solvo)thermal method and structurally characterized by single-crystal X-ray diffraction. Interestingly, the perspective view of the crystal structure for NTOU-2S is similar to our previous report of NTOU-2 but the carboxylate organic ligands (TPDC for NTOU-2S; 1,4-benzenedicarboxylate, BDC, for NTOU-2) in both compounds adopt different types of bis-monodentate coordination models (the unusual cis bonding versus a trans linkage) to bridge the metal atoms of inorganic tubes in the formation of large-channel zincophosphite frameworks, resulting in structural and functional diversities. The thiophene-based compound also displayed higher thermal stability and removal ability for the softer Hg2+ cations from water solutions than the performance of sulfur-free NTOU-2. In addition, the synthesis, structural characteristics, removal properties of heavy metal cations, and thermal and chemical stabilities for both compounds were also reported.