Structure Investigation and Electrochemical Behavior of GAMMA-MnO2 Synthesized from Three-Dimensional Framework and Layered Structures

Introducing cobalt into the Zn-P-O-amine system and using oxalates as starting materials, an amine-containing open-framework zinc cobalt phosphate, [C2N2H10] [Co4.2Zn1.8 (PO4)4(HPO4)]·H2O (1), has been hydrothermally synthesized. It crystallizes in monoclinic space group C2/c (No. 15) with cell parameters a=19.214(8) ?, b=5.0152(17) ?, c=21.175(8) ?, BETA=103.06(3)°, V=1987.7(13) ?3, Z=4, Dcal=3.078 g cm-3. The structure contains two sets of M-O-M linkage: M-O-M dimer and unusual infinite helical &-M-O-M- chain. Connecting the dimers by phosphates leads to three-membered ring chains. The linking of the helical chains by PO4 groups results in a sheet structure. Using the three-membered ring chains as pillars, stacking of the sheets gives rise to a three-dimensional tunnel structure.