Design of Novel Bilayer Compounds of the CPO-8 Type Containing 1D Channels

The reaction between Zn(NO3)2·6H2O and 5-aminoisophthalic acid (aip) in a mixture of diethylformamide (DEF)
and ethanol resulted in [Zn(C8H5NO4)(C5H11NO)]n (CPO-8-DEF). This compound is composed of infinite 2D layers
with tetrahedral Zn atoms and aip ligands in a triangular topology. The DEF molecules are bonded to Zn, and
within each layer, the DEF molecules are oriented in the same direction, while in the subsequent layer, the DEF
molecules are oriented in the opposite direction. By introduction of the pillaring ligands 4,4-bipyridine (BPY), 1,2-di-4-pyridylethylene (DPE), 1,2-di-4-pyridylethane (DPA), and 1,3-di-4-pyridylpropane (DPP) into mixtures of N,N‘-dimethylformamide and water with Zn(NO3)2 and aip, we have successfully synthesized a series of related pillared
bilayer compounds with the same common triangular Zn(aip) layer structural motif as that observed in CPO-8-DEF.
The compounds are denoted as CPO-8-BPY ([Zn(C8H5NO4)(C10H8N2)0.5]n·3nH2O), CPO-8-DPE ([Zn(C8H5NO4)(C12H10N2)0.5]n·2.5nH2O), CPO-8-DPA ([Zn(C8H5NO4)(C12H12N2)0.5]n·2.5nH2O), and CPO-8-DPP ([Zn(C8H5NO4)(C13H14N2)0.5]n·3nH2O). In all cases, the pillars create spaces inside the bilayers that result in 1D channels running
along the [010] directions with dimensions of 3.5 × 6.7 Å2. These channels contain water molecules that can be
removed on heating to 150 °C, resulting in porous structures. The crystal structures of these porous high-temperature
variants have been determined on the basis of powder X-ray diffraction data. All of the compounds show preferential
adsorption of H2 over N2 at 77 K.