Synthesis of a Chiral 3,6T22-Zn-MOF with a T-Shaped Bifunctional Pyrazole-Isophthalate Ligand Following the Principles of the Supramolecular Building Layer Approach

Abstract

The metal–organic framework (MOF) [Zn(Isa-az-tmpz)]·~1–1.5 DMF with the novel T-shaped bifunctional linker 5-(2-(1,3,5-trimethyl-1H-pyrazol-4-yl)azo)isophthalate (Isa-az-tmpz) was obtained as a conglomerate of crystals with varying degrees of enantiomeric excess in the chiral tetragonal space groups P43212 or P41212. A topological analysis of the compound resulted in the rare 3,6T22-topology, deviating from the expected rtl-topology, which has been found before in pyrazolate-isophthalate-functionalized MOFs using the supramolecular building layer (SBL) approach. 3,6T22-[Zn(Isa-az-tmpz)]·~1–1.5 DMF is a potentially porous, three-dimensional structure with DMF molecules included in the corrugated channels along the a and b-axis of the as synthesized material. The small trigonal cross-section of about 6 × 4 Å (considering the van der Waals surface) prevents the access of N2 and Ar under cryogenic conditions. After activation, only smaller H2 (at 87 K) and CO2 (at 195 K) are allowed for gas uptakes of 2 mmol g–1 and 5.4 mmol g–1, respectively, in the ultramicroporous material, for which a BET surface area of 496 m2·g–1 was calculated from CO2 adsorption. Thermogravimetric analysis of the compound shows a thermal stability of up to 400 °C.