Modular Assembling of [Zr(C₂O₄)₄]⁴⁻ and [DabcoH₂]²⁺ Units in Supramolecular Hybrid Architectures Including an Open Framework with Reversible Sorption Properties (Dabco = 1,4-Diazabicyclo[2. 2. 2]octane)

An emerging trend toward development of metal-organic frameworks (MOF) consists in using preformed complexes as building blocks able to assemble via coordination chemistry and/or charge-assisted H-bonding. Within this framework and depending only on the experimental conditions, reactions of the [Zr(C2O4)4]4− anion with the [DabcoH2]2+ dication (Dabco = 1,4-diazabicyclo[2. 2. 2]octane) selectively afford the compounds {K2(DabcoH2)[Zr(C2O4)4]}·6.5H2O (1), {(DabcoH2)2[Zr(C2O4)4]}·3H2O (2), {(DabcoH2)2[Zr(C2O4)4]}·5.5H2O (3), or {K2(DabcoH2)2[Zr2(C2O4)7]}·6H2O (4). Three association schemes exhibiting drastically different network topologies have been characterized ranging from 1D to 3D; the fourth involving the in situ generated bimetallic {Zr2(C2O4)7}6− moiety. For all four compounds, selective synthetic processes have been developed. In addition, compound 1 exhibits an open framework able to release solvates without collapsing. Besides the reversible sorption of small molecules like EtOH and MeCN, the open framework 1 was found to adsorb CO2 at ambient temperature and pressure (ca. 30 cm3 of gas g−1 at 298 K), whereas its propensity to take up H2O from air is low.