Aluminum-1,4-cyclohexanedicarboxylates: high-throughput and temperature-dependent in situ EDXRD studies

The system AlCl3·6H2O/cis-H2CDC/trans-H2CDC/solvent was systematically investigated with high-throughput methods to study the influence of the two 1,4-cyclohexanedicarboxylate isomers (cis- and trans-H2CDC) as flexible aliphatic linker molecules on the formation of new crystalline compounds. Using the cis-isomer, the layered inorganic-organic hybrid compound [Al(OH)(cis-CDC)] (1) is formed. The use of trans-H2CDC leads to the microporous MOF [Al(OH)(trans-CDC)]·H2O (2) denoted CAU-13. Its framework is related to the well-known MIL-53, which was previously described for trivalent cations and rigid terephthalate linker molecules. The crystal structures of 1 and 2 were derived from powder X-ray diffraction data. Temperature-dependent in situ energy dispersive X-ray diffraction (EDXRD) experiments for the synthesis of 2 were carried out at HASYLAB, DESY, Hamburg. The kinetic analysis, applying the Gualtieri model to the experimental data, revealed Arrhenius activation energies of 76 kJ/mol for both the nucleation and the growth process. These values do not differ much from the activation energies reported for MOFs with aromatic rigid linker molecules.