New Open-Framework Zinc Oxalates Synthesized in the Presence of Structure-Directing Organic Amines

Abstract

Two new open-framework zinc oxalates have been prepared by hydrothermal methods in the presence of structure-directing organic amines. The crystal data for these oxalates are as follows: I, [H3N(CH2)(3)NH3](2+)[Zn-2(C2O4)(3)](2-). 3H(2)O, triclinic, space group P (1) over bar (no. 2), a = 9.261(1) Angstrom, b = 9.455(1) Angstrom, c = 12.487(1), alpha = 83.93(1)degrees, beta = 88.01(1)degrees, gamma = 61.03(1)degrees, V = 951.1(1) Angstrom(3), Z = 2, M = 524.8, D-calc = 1.83 g cm(-3), mu = 2.60 mm(-l), Mo K alpha, R-F = 0.03; II, 2[C3H7NH3](+)[Zn-2(C2O4)(3)](2-). 3H(2)O, monoclinic, space group C2/c (no. 15), a = 15.847(1) Angstrom, b = 9.685(1) Angstrom, c = 18.333(1), beta = 115.5(1)degrees, V = 2539.1(2) Angstrom(3), Z = 4, M = 569.1, D-calc = 1.60 g cm(-3), mu = 1.97 mm(-1), Mo K alpha, R-F = 0.07. In I, the linkages between the Zn and oxalate units gives rise to a layered architecture with 12-membered (6 Zn and 6 oxalates) honeycomblike apertures wherein the amine and water molecules are located. In II, the Zn-oxalate layers are cross-linked by another oxalate unit giving rise to a three-dimensional structure with two distinct channels where the amine and water molecules reside; the largest aperture in II involves a 20-membered ring (10 Zn and 10 oxalates). There is extensive hydrogen bonding among the amine, water, and the framework. Adsorption studies indicate that water can be reversibly adsorbed in I.