Dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate was introduced into the chemically stable UiO-66 structure by a postsynthetic linker exchange reaction to create an optical sensor material for the detection of oxidative agents such as nitrous gases. The incorporated tetrazine unit can be reversibly oxidized and reduced, which is accompanied by a drastic colour change from yellow to pink and vice versa. The high stability of the framework during redox reaction was proven by powder X-ray diffraction and nitrogen physisorption measurements.