Missing linkers during the co-assembly process offer open metal sites, which facilitate cycloaddition catalysis. The defects inside ZIF can be determined using several techniques such as temperature-programmed desorption (TPD), high-resolution transmission electron microscopy (HR-TEM), and thermogravimetric analysis (TGA). ZIF-8 with uncoordinated N-sites on the framework showed a high chemical fixation of CO2 . Unfortunately, so far, the defects in the frameworks are uncontrollable and lack high reproducibility.