The role of solvents in framework dimensionality and their effect on band gap energy

• Published in: Dalton transactions : an international journal of inorganic chemistry 2015-01, Vol.44 (3), p.1009-1016
• Main Authors: Asha, K S, Kavyasree, P R, George, Anu, Mandal, Sukhendu
• Format: Article
• Language: English
• Subjects: Cadmium; Chains; Clusters; Energy gap; Linkages; Morphology; Solvents; Trimers; Tuning
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt01678e

The crystal growth rate and morphology can be modulated by tuning the ratio of the solvent in mixed solvents during synthesis. We present here a solvothermal method to synthesize a Cd-FDC based metal-organic framework with different morphologies by tuning the ratio of water in the DMF-water mixed solvent system without adding any other additives. With the increasing water volume ratio a series of crystals with different morphologies were synthesized. Among these we have isolated two single crystal structures, [Cd3(FDC)3(DMF)4(H2O)], and [DMA]2[Cd3(FDC)4]·2H2O, . Compound was synthesized from DMF with small amounts of water while was formed from 25 vol% of water in the DMF-water mixed solvent. Compound contains trimer clusters as building units, which are linked by the furan dicarboxylate ligand to form a two-dimensional structure. Compound also contains trimer clusters which are linked to each other to form a one-dimensional chain with the Cd-O-Cd linkage. This one-dimensional chain in turn is connected by the furan dicarboxylate ligand to form a three-dimensional structure. All these structures are characterized by SEM, XRD, TGA and IR. We have measured the band gap energy and measurements show that the values are decreasing from to . The lower band gap energy of may be due to the presence of infinite Cd-O-Cd linkages which split the states of the conduction band and reduces the band gap energy.