Microporous hybrid compounds:: hydrothermal synthesis and characterization of two zinciomethylenediphosphonates with 3D structures, structure determination of their dehydrated forms

The ZnCl2-H2O3P-CH2-PO3H2-NaOH-H2O quaternary system was investigated under hydrothermal conditions as a function of pH (48 h; 443 K). Zn-2(H2O){O3P-CH2-PO3}(labelled VSB-3(Zn)) and NaZn2(OH){O3P-CH2-PO3}.1.5H(2)O (labelled MIL-48) are obtained at pH 1 and 9 respectively. Their structures were solved from single crystal X-ray diffraction. Zn-2(H2O){O3P-CH2-PO3}, isostructural with Co and Ni analogues previously described, is monoclinic (C 2/c (nu 15)) with lattice parameters a = 18.7573(3) Angstrom, b = 8.2803(2) Angstrom, c = 8.9225(1) Angstrom, beta = 106.815(1)degrees, V = 1326.56(4) Angstrom(3), Z = 8, R1(F-o) = 0.0269 and wR2(F-o(2)) = 0.0704 for 1735 unique reflections I greater than or equal to 2sigma(I). Its thermal evolution first leads to anhydrous Zn-2{O3P-CH2-PO3} (labelled VSB-4(Zn)) whose structure was refined from XRD powder pattern, then to c and beta zinc diphosphates successively. NaZn2(OH){O3P-CH2-PO3}.1.5H(2)O is monoclinic (P2(1)/c (ndegrees 14)) with lattice parameters a = 8.9929(9) Angstrom, b = 5.5093(6) Angstrom, c = 18.025(2) Angstrom, beta = 92.376(2)degrees, V = 892.3(2) Angstrom(3), Z = 4, R1(F-o) = 0.0700 and wR2(F-o(2)) = 0.1078 for 2358 unique reflections I greater than or equal to 2sigma(I). Its three-dimensional structure provides a new zeotype with 10-membered channels where the Na+ cations and the water molecules are encapsulated. The elimination of water provides a new compound, NaZn2(OH){O3P-CH2-PO3} (labelled MIL-48(calc)), whose structure was refined from XRD powder pattern.