A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 × 3 nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++) 2-carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.
Bibliographical noteFunding Information:
We thank Ms. Hülsmann, Bielefeld University, for the preparation of P(EP)2DC. Financial support by Deutsche Forschungsgemeinschaft (DFG) within the Priority Program Metal-Organic Frameworks (SPP 1362) is gratefully acknowledged. T.H. acknowledges financial support by the European Research Council (GA ERC-StG-256962 C3ENV).
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