[note: Figures are in the source article and not highlighted in this summary]

This is a summary of work reported in the Journal of Inorganic Chemistry concerning crystallin inorganic-organic frameworks and their properties. In the literature, is is obvious that crystalline open frameworks have many potential uses in the storage of gases, magnetism, and catalytic reactions.¹ These possible applications have driven an increasing amount of research into their development. There are abundant types of inorganic and organic frameworks (IF, OF) which have been developed. Included within these categories are zeolites, or aluminosilicate frameworks typically used as molecular sieves, transition-metal phosphate structures, and metal-organic framework (MOFs) structures.¹

These frameworks heave been heavily studied and MOFs and IFs are viewed as the two most important types of porous material frameworks currently being researched.¹ Hybrid structures using elements from both inorganic and metal-organic frameworks are less known.¹ The authors in this study are expressly interested in these specific types of hybrid structures, primarily focusing on Cobalt based organometallophosphates (OMPOs) and their potential uses in catalytic and redox chemical reactions.¹

Classification of these organic-inorganic frameworks may be classified using the Cheetham system in the following IⁿO^m format, where n,m are integers from 0, and I and O refer to the frameworks inorganic, and organic, dimensions in reference to M-X-M and M-L-M connectivity (X denoting O, N, Cl, or S, and L being an organic ligand). Most hybrid frameworks have dimensionalities from 0 to 3. Super-imposed dimensionalities over 3 are rare.¹

Two new hybrid frameworks, developed using a solvothermal reaction of CoCl₂*6H₂O, DABCO, H₃PO₄, and H₂bpdc in N,N-dimethylformamide (DMF), (where DABCO is 1,4-diazobicyclo [2.2.2] octane, and bdpc is 4,4`-biphenyldicarboxylate) are reported by the authors, with first compound (C1) using the bpdc ligand, and the second compound (C2) using the npa ligands. The compounds C1 framework: [H₂DABCO] x [Co(HPO₄)(bpdc)] and the compound C2 framework: [H₂DABCO]₃ x [Co₁₀(npa)₃(HPO₄)₆Cl₂].

Structurally, C1 exhibits a layered inorganic Co(HPO₄) matrix, with the cobalt-phosphate braced by the bpdc ligands. The matrix is held together by hydrogen bonds formed between the ligands and cations.¹ In figure 1 the authors break down the Co(HPO₄) subunits into a basic 4-node layout illustrating it’s tetrahedral geometry. This tetrahedral geometry seen in the subunit is multiplied across the matrix and is responsible for creating the ABW topology seen in (d) of figure 1.

C2’s structure exhibits a metal phosphate layer and metal organic layer connected by their Co₅ and Co₄ clusters into a hexagonal pattern, with the Co₄ clusters having a more exaggerated twist to their structure comparatively. In part (c) of Figure 2, C2’s bilayer and its interlocking framework are illustrated. In part (d) the DABCO groups are illustrated from the z-axis viewpoint down the channels formed from the hexagonal geometry. C2’s main geometric feature of interest is its unusual honeycomb formation, as it allows for the compounds classification of I²O² which means that it has a dimensionality of 4, above the typical 3 often seen.¹ C1 in comparison is an I²O⁰ framework with a dimensionality of 2, which is traditional.¹

With this structural analysis of C1 and C2, and by obtaining and calculating the magnetic susceptibility data through the Curie-Weiss law for the Co^II ions, the authors were able to demonstrate two new OMPO compounds. The most important of which is C2 exhibiting its atypical dimensionality, and the proof that Cobalt ions with multiarylcarboxylate-type ligands are sturdy OMPO constituents.

Summary: 2/13/2016

References

1. Ding, Q., Li, L., Zhang, L., Zhang, J.; Multiarylcarboxylate-mediated Hybrid Cobalt Phosphate Frameworks with Supramolecular Zeolitic Topology and unusual I²O² Connectivity, J. Inorganic Chemistry, 2015, 54, 1209-1211.