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

Abstract

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(NO 3 ) 2 •6H 2 O and H 3 pzdc with 4-(pyridin-4-yl)-1H-pyrazole (Hpypz), 1,4-benzenedicarboxylic acid (H 2 bdc), or 2amino-1,4-benzenedicarboxylic acid (H 2 abdc) in a mixed solvent of H 2 O and N,N-dimethylformamide (DMF) produced three pillared-layer PCPs, namely [Zn 4 (pzdc) 2 (pypz) 2 ]•guest (1), [Zn 4 (pzdc) 2 (bdc)(H 2 O) 1. 5 3 (DMF) 0. 4 7 ]•guest (2), and [Zn 4 (pzdc) 2 (abdc)(H 2 O) 1.52 (DMF) 0.48 ]•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 CO 2 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 (H 2 O) 6 ]•H 2 bdc•4H 2 O (4) and [Zn 4 (pzdc) 2 (H 2 abdc)(OH) 2 (H 2 O) 5 ]•2H 2 O (5), respectively, which can be further exfoliated into ultrathin nanosheets in an ammonia solution.