Aldehyde-tagged UiO-67-type metal organic frameworks (MOFs) have been synthesized via the direct solvothermal-method or postsynthetic ligand exchange. Various functionalities have been introduced into the MOFs via postsynthetic modification (PSM) employing C-N and C-C coupling reactions of the aldehyde tag. Tandem PSM has also been demonstrated. An amino-functionalized MOF obtained by PSM is shown. to be an efficient, heterogeneous, and recyclable catalyst for Knoevenagel condensation.