Synthesis of two-dimensional metal–organic networks from 1,10-phenanthroline-chelated cadmium complex and polycarboxylate

Abstract The design of two 2D metal–organic frameworks using a 1,10-phenanthroline-chelated cadmium complex as precursor and a bridging polycarboxylate as linker is described. The reaction of Cd(NO 3 ) 2 ·4H 2 O with the chelating ligand 1,10-phenanthroline (phen) at room temperature gave [Cd(phen)(NO 3 ) 2 ] ( 1 ) in high yield. Treatment of the inorganic precursor 1 with the polycarboxylate bridge ligand, benzene-1,4-dicarboxylic acid (H 2 BDC) or benzene-1,2,4,5-tetracarboxylic acid (H 4 btec), under mild hydrothermal conditions led to the formation of two metal–organic networks {[Cd(BDC)(phen)]·DMF} n ( 2 ) and [Cd 2 (btec)(phen) 2 ] n ( 3 ). Single-crystal X-ray diffraction analyses showed that both products have two-dimensional sheet architectures. Compound 2 was constructed via the use of [Cd 2 (O 2 C ) 4 ] unit and BDC linker, whereas compound 3 involved the use of [CdO 4 ] core and btec bridge. The cadmium ions in compounds 2 and 3 are hepta- and hexa-coordinated, respectively. Thermogravimetric (TG) analyses showed that 2 and 3 are thermally stable ( T decomp.  > 360 °C). Photoluminescence studies revealed that compounds 1 – 3 displayed a strong fluorescent emission in the solid state at room temperature.