Figure 2 (a) TGA curve of Ni(TMBDC)(DABCO)0.5; (b) PXRD patterns of Ni(TMBDC)(DABCO)0.5 before and after various treatment.
TGA data were collected for the evaluation of the thermal stability of the Ni(TMBDC)(DABCO)0.5. Figure 2(a) presents the TGA curve of Ni(TMBDC)(DABCO)0.5. It is noticed that the TGA curve showed a negligible weight loss (~5%) before 400 ºC which was attributed to the removal of guest molecules such as H2O molecule. After 400 °C, a great weight loss (~68%) occurred due to the decomposition of the framework structure. It suggests that the Ni(TMBDC)(DABCO)0.5 is thermally stable until 400 ºC.
We also examined the solvent stability and water vapor stability of the Ni(TMBDC)(DABCO)0.5. Figure 2(b) shows the PXRD patterns of Ni(TMBDC)(DABCO)0.5 before and after soaking in various solvents or exposure to humid air for several days. It is visible that the Ni(TMBDC)(DABCO)0.5 retained the structural integrity after soaking separately in acetone, DCM, Hexanes for 4 days and ethanol for 20 days, demonstrating excellent stability in these organic solvents. Furthermore, the water vapor stability was tested by exposing the Ni(TMBDC)(DABCO)0.5 to humid air with 55% and 100% humidity for 4 days. The PXRD patterns of Ni(TMBDC)(DABCO)0.5 after exposure to humid air are similar to that of the fresh material, suggesting its excellent humid stability. The water vapor stability could be attributed to the hydrophobicity of the channel of Ni(TMBDC)(DABCO)0.5, which is caused by the methyl group on the TMBDC ligand and the methylene group on the DABCO ligand.