Synthesis, Characterization and Phase Transformation of 3D Open-framework Zinc Phosphate [Zn6（H2O）P5O20] [C5N2H14] [C6H16N2]0.5·3H2O

With N,N′-dimethylpiperazine（DMPIP） as the structure-directing agent, a zinc phosphate [Zn6（H2O）P5O20] [C5N2H14] [C6H16N2]0.5·3H2O（1） with a novel three-dimensional（3D） open-framework architecture was hydrothermally synthesized. Its structure was determined by single-crystal X-ray diffraction analysis and further characterized by ICP, NMR, and TG analyses. Compound 1 crystallized in the triclinic space group P1（No.2） with a=0.9984（2） nm, b=1.2354（3） nm, c=1.2384（3） nm, α=88.32（3）°, β=74.57（3）°, γ=75.81（3）° and Z=2. The alternation arrrangement of tetrahedral Zn units[ZnO4 and ZnO3（H2O）] and PO4 units forms an anionic 3D open framework containing intersecting 16-, 10- and 8-ring channels. Water molecules, diprotonated DMPIP, and diprotonated N-methyl-piperazine（MPIP） decomposed from DMPIP, are located in the channels and interact with the host framework via H-bonds. Compound 1 transforms to another new phase（compound 2） upon calcination at 200―350℃ with the removal of the water coordinated to Zn atoms in the lattice. The phase transformation of compound 2 was further studied.