Family of Isoreticular Chiral Metal−Organic Frameworks Based on Coordination and Hydrogen Bonds in [M[Co(ethylenediamine)(oxalato)2]2].

From the parent compound [Ca[Co(ethylenediamine)(oxalato)2]2]n·4H2O, 1, a series of framework compounds was prepared via the soluble sodium salt and crystal growth with the divalent metal ions Cd2+, Mn2+, and Sr2+, (2−4). These compounds have the same general formula [M[Co(ethylenediamine)(oxalato)2]2]n·xH2O, and they all form the same four- and eight-connected 3D net having scu topology (and are thus isoreticular) with water filled channels of variable size running in one direction of the crystals. However, they crystallize in two different space groups, the chiral P21 (3, 4, and the low temperature form of 1) and the noncentrosymmetric P4̅ (1 and 2). The potential voids upon water removal are 18−20% of the unit cell. Preliminary gas sorption measurements at 298 K and 8 bar show substantial CO2 and N2O uptake (12−14% and 15−16% by mass, respectively), while the H2 uptake was 0.18%, a relatively high value considering the low pressure and high temperature. A MOF series with formula [M[Co(en)(ox)2]2]n·4H2O, M = Ca2+, Cd2+, Mn2+, Sr2+ are presented. These form the same 3D scu-nets with water filled channels of variable size. For Ca2+ gas sorption (298 K, 8 bar) show CO2 and N2O uptake of 13% and 14% by mass, while H2 uptake was 0.18%, a relatively high value considering the pressure and temperature. [ABSTRACT FROM AUTHOR]