Synthesis, structure, luminescence and catalytic properties of cadmium(ii) coordination polymers with 9H-carbazole-2,7-dicarboxylic acid

Two Cd(ii) metal-organic frameworks were synthesized from the NH-functionalized dicarboxylate ligand 9H-carbazole-2,7-dicarboxylic acid (2,7-H₂CDC). Compound 1, [Cd₄(CDC)₄(DMF) ₄]·4DMF·4H₂O, displays 2D square grid networks based on novel tetranuclear [Cd₄(COO)₈] secondary building units (SBUs) and pairwise CDC^2- linkers. Compound 2, (H₃O)₂[Cd₃(2,7-CDC)₄] ·3DMF·4H₂O, is also based on 4-connected SBUs and pairwise CDC linkers, but the unusual trinuclear [Cd₃(COO) ₈] SBUs lead to 2-fold interpenetrated 3D diamond-type frameworks with guest accessible voids. Both compounds display strong blue fluorescence in the solid state, and compound 2 shows high catalytic activity for Knoevenagel condensation.