Hydrothermal synthesis and structure of an open framework Co0.7Zn1.3(PO4)2(NH3–CH2CH2NH3) and Co6.2(OH)4(PO4)4Zn1.80, a new adamite type phase

The hydrothermal reaction of cobalt(II)oxalate di-hydrate, zinc oxide, and triethyl-orthophosphate, using 1,2-diaminoethane as structure directing template in water, produced two major crystal phases in almost equal amount: the purple crystals of [NH3–CH2CH2NH3][Co0.7Zn1.3(PO4)2] (1) and the red burgundy crystals of Co6.2(OH)4(PO4)4Zn1.80 (2), a new adamite type phase. The structure of [NH3–CH2CH2NH3] [Co0.7Zn1.3(PO4)2] (1) exhibits a 3D open framework built from PO4 and (Co/Zn)O4 tetrahedra, and (Co/Zn)O5 trigonal bipyramids, forming two major channels, an 8-membered ring channel and a 16-membered ring channel, that host the ethanediammonium ions. The Co6.2(OH)4(PO4)4Zn1.80 (2) is isomorphous with adamite-type M2(OH)XO4 structure, with a condensed vertex and edge sharing network of (Co/Zn)O5, and distorted CoO6, and PO4 subunits. The cobalt preference for higher coordination numbers is displayed in this structure, where the octahedral sites are wholly occupied by cobalt. Thermal analysis confirmed that these compounds display high thermal stability.