Hydrothermal synthesis and structure of an open framework Co 0.7Zn 1.3(PO 4) 2(NH 3–CH 2CH 2NH 3) and Co 6.2(OH) 4(PO 4) 4Zn 1.80, a new adamite type phase

Abstract

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 [NH 3–CH 2CH 2NH 3][Co 0.7Zn 1.3(PO 4) 2] ( 1) and the red burgundy crystals of Co 6.2(OH) 4(PO 4) 4Zn 1.80 ( 2), a new adamite type phase. The structure of [NH 3–CH 2CH 2NH 3] [Co 0.7Zn 1.3(PO 4) 2] ( 1) exhibits a 3D open framework built from PO 4 and (Co/Zn)O 4 tetrahedra, and (Co/Zn)O 5 trigonal bipyramids, forming two major channels, an 8-membered ring channel and a 16-membered ring channel, that host the ethanediammonium ions. The Co 6.2(OH) 4(PO 4) 4Zn 1.80 ( 2) is isomorphous with adamite-type M 2(OH)XO 4 structure, with a condensed vertex and edge sharing network of (Co/Zn)O 5, and distorted CoO 6, and PO 4 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.