A 3D Porous Cobalt−Organic Framework Exhibiting Spin-Canted Antiferromagnetism and Field-Induced Spin-Flop Transition

Two 3D cobalt−organic frameworks formulated as [Co3(2,4-pydc)2(μ3-OH)2]n·5nH2O (1) and [Co3(2,4-pydc)2(μ3-OH)2(H2O)]n·7nH2O (2) (2,4-pydc = pyridine-2,4-dicarboxylate) have been hydrothermally synthesized and
characterized. Both compounds 1 and 2 exhibit the 3D porous frameworks with hydroxyl-bridged metal Δ-chains.
However, in comparison with only two crystallographically independent CoII ions in a unit of 2, three crystallographically
independent CoII ions are found in an asymmetric unit of 1, where their Δ-chains are constructed by two types of
vertexes sharing quadrangles formed via edge-sharing triangles. Magnetic studies show that 1 exhibits spin-canted
antiferomagnetism and a field-induced spin-flop transition while 2 behaves as a normal antiferromagnet. The magnetic
properties are largely retained by the porous frameworks of dehydrated 1 and 2 compounds. Gas adsorption
measurements indicate that both the dehydrated compounds absorb H2 into their pores.