Synthesis and characterization of a new metal organic framework structure with a 2D porous system: (H2NEt2)2[Zn3(BDC)4]⋅3DEF

A new open-framework zinc terephthalate (H2NEt2)2[Zn3(BDC)4]⋅3DEF (BDC = 1,4-benzendicarboxylate, DEF=N,N′DEF=N,N′-diethylformamide) was obtained under slightly acidic condition by reacting 1,4-benzendicarboxylic acid (H2BDC) with ZnO in a DEF solution.The structure was obtained by single crystal X-ray diffraction and consists of trimetallic zinc building units, that are interconnected by eight BDC units each (crystal data: monoclinic, C2/cC2/c, a=3337.24(5)a=3337.24(5), b=983.17(2)b=983.17(2), c=1819.67(2) pmc=1819.67(2) pm, β=92.455(1)○β=92.455(1)○, V=5965.0(2)×106 pm3V=5965.0(2)×106 pm3, Z=4Z=4, R1=0.0395R1=0.0395, wR2=0.0843wR2=0.0843 for 4533 reflections I>2σ(I)I>2σ(I)). Six BDC ions together with the trimetallic zinc units form a two-dimensional (3,6)(3,6)-net while the other two BDC unit pillar these layers. Thus a three-dimensional anionic framework with a 2D pore system is formed. The pore space is occupied by solvent molecules (DEF) and diethylammonium ions, produced by in situ hydrolysis of DEF. These are interconnected as well as connected to the framework by hydrogen-bonds. The TG investigation in combination with powder X-ray diffraction and vibrational-spectroscopy show a two-step loss of the pore filling molecules as well as one H2BDC molecule leading to crystalline phases which are stable up to 250 and 400 °C, respectively. In addition, 13C MAS-NMR data of the title compound is presented.

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