Two Six-Connected MOFs with Distinct Architecture: Synthesis, Structure, Adsorption, and Magnetic Properties.

By assembling Co ions and a combination of 5-(4-pyridyl)tetrazole (4-ptz) and formate ions, two distinct metal-organic frameworks, [Co (4-ptz) (HCOO)(H O) ] and [Co (4-ptz) (dmf) (HCOO) ] (dmf=N,N'-dimethylformamide), were synthesized. They were both characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Structural analyses revealed that by slightly modulating the coordination environment of the trinuclear cobalt cluster, two complexes were formed featuring unusual six-connected nets reminiscent of a pyrazole-type linear trinuclear cobalt cluster as compared with the classic eight-connected bcu topology. In addition, [Co (4-ptz) (HCOO)(H O) ] interacted strongly with CO , with an adsorption enthalpy of 29.2 kJ mol , and in a selectivity study, the uptake ratios of CO /N (from a 15:85 mixture) and CO /CH (50:50 mixture) were 77.6 and 37.7, respectively. Magnetic studies on both complexes revealed weak antiferromagnetic coupling between the Co ions.