Isoreticular MOFs derived from arylphosphonate linkers

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The synthesis of metal-organophosphonate compounds (MOPh) by design is the ultimate goal of scientists working in the field of metal organic frameworks (MOFs). Metal-organophosphonate MOFs exhibit excellent chemical stability and they are less air sensitive compared to the conventional carboxylate MOFs. However, the reticular chemistry of MOPhs has not been developed yet and no isoreticular expansions have been reported using the metal-arylophosphonate chemistry to produce materials with predictable pore sizes. The ability to introduce predictable pore sizes into MOPh chemistry will create tremendous potential in medicinal and material applications etc. The structure and geometry of the bridging ligand is the most important factor determining the final structure of the MOFs. To establish the basics of MOPh reticular chemistry, linker molecules with different tether lengths and three-dimensional geometries need to be explored. To date, systematic studies to establish the reticular chemistry of MOPhs have not been conducted. Therefore, we have designed three complimentary geometries (denoted V, Y, X) of organophosphonate linkers with increasing tether lengths to study their metal complexes, to create predictable pores with selected transition metals ions plus Zn, Al and Ca metal ions. The first group of linkers is composed of V-shaped arylphosphonates including 1,2-bis(p-phosphonatophenyl)benzene, 1,2-bis(p-phosphonatobisphenyl)benzene and 1,2-bis(p-phosphonatoterphenyl)benzene and also at 1,3- positions. The Y-shaped second linker geometry includes the ligands 1,3,5-tris-(4-phosphonophenyl)benzene, 1,3,5-tris-(4-phosphonobisphenyl)benzene and 1,3,5-tris-(4-phosphonoterphenyl)benzene. The third group includes planar X-shaped tetratopic phosphonate ligands based on the porphyrine core and tetrahedral X-shaped linkers based on methane and silane cores expanding into three dimensions. The X-shaped linkers based on planar porphyrine core expanding in two dimensions include meso-tetra(4-phosphorylphenyl) porphine, meso-tetra(4-phosphorylbisphenyl) porphine, and meso-tetra(4-phosphorylterphenyl) porphine, and the fourth group of linkers have tetrahedral methane and silane cores expanding into three-dimensions, which includes methane tetra-p-tetraterphenylphosphonic acid, methane tetra-p-tetrabiphenylphosphonic acid, methane tetra-p-phenylphosphonic acid and their silane derivatives. This study will be the first systematic approach to establish the reticular chemistry of MOPh compounds using the arylphosphonate linkers by gradually extending their tether lengths. The synthesis of proposed linkers and their systematic structural studies with transition metal ions, zinc and aluminum will be carried using hydrothermal and solvothermal synthesis. Single crystal and powder X-ray diffraction will be used to reveal the MOPh crystal structures and BET analysis for the promising ones will be conducted. Proton conducting properties will be investigated.