An ionothermally synthesized Mg-based coordination polymer as a precursor for preparing porous carbons

A new magnesium coordination polymer (Mg-CP), namely [Bmim]₂[Mg₆(NDC)₅(HNDC)₂(HCOO)₂] (1, H₂NDC = 1, 4-naphthalenedicarboxylic acid, [Bmim] = 1-butyl-3-methyl-imidazolium ion), has been ionothermally synthesized and structurally characterized. Single-crystal X-ray structural determination indicated that the title compound possessed an anionic three-dimensional (3D) framework constructed by the interconnections of unprecedented hexanuclear magnesium-carboxylate clusters as secondary building units (SBUs) via bridging NDC ligands. Compound 1 exhibited blue luminescence emission at 440 nm when excited at 360 nm. Significantly, the title non-porous Mg-CP could be utilized as a precursor for preparing porous carbons through thermal decomposition in optimized conditions. Different from the reported high decomposition temperature (>1000 °C) mostly based on porous Zn-CP precursors, the optimum decomposition temperature for 1 was only 700 °C, and the resulting porous carbons showed 465 cm³ g^-1 adsorption volume for N₂. The as-prepared carbon exhibited finely selective N₂ adsorption ability over H₂ and CO₂. This work may provide a certain guiding significance for exploiting ionothermally synthesized Mg-CPs as a new type of precursor towards porous carbons.