A Metal-Ligand Layer Compatible with Various Types of Pillars for New Porous Coordination Polymers

Pillared-layer structures are classic for porous coordination polymers (PCPs), but suitable metal-ligand layers for such structures are rare. Here, we report a cationic {Zn-2(pzdc)}(+) (H(3)pzdc = 3,5-pyrazoledicarboxylic acid) layer compatible with various types of pillar ligands. Solvothermal reactions of Zn(NO3)(2)center dot 6H(2)O and H(3)pzdc with 4-(pyridin-4-yl)-1H-pyrazole (Hpypz), 1,4-benzenedicarboxylic acid (H(2)bdc), or 2-amino-1,4-benzenedicarboxylic acid (H(2)abdc) in a mixed solvent of H2O and N,N-dimethylformamide (DMF) produced three pillared-layer PCPs, namely [Zn-4(pzdc)(2)(pypz)(2)]center dot guest (1), [Zn-4(pzdc)(2)(bdc)(H2O)(1.53)(DMF) 0.47]center dot guest (2), and [Zn-4(pzdc)(2)(abdc)(H2O)(1.52)(DMF)(0.48)]center dot guest (3), respectively. Single-crystal X-ray analyses revealed that the {Zn-2(pzdc)}(+) layers are fully pillared by pypz- in 1 and half pillared by bdc(2-) and abdc(2-) in 2 and 3, because the anionic pillars possess different charges. Consequently, 1 shows one-dimensional (1D) channels with a small porosity and 2 and 3 show 2D channels with large porosities, both of which were verified by N-2 and CO2 adsorption isotherms. While 1 has no coordinated solvent molecules and exhibits a high water stability, 2 and 3 possess coordinated solvent molecules and quickly transform to crystals of 2D coordination networks in water, [Zn-4(pzdc)(2)(OH)(2)(H2O)(6)]center dot H(2)bdc center dot 4H(2)O (4) and [Zn-4(pzdc)(2)(H(2)abdc)(OH)(2)(H2O)(5)]center dot 2H(2)O (5), respectively, which can be further exfoliated into ultrathin nanosheets in an ammonia solution.yy