Blue-light emitting cadmium-based 2D metal–organic frameworks derived from cis-5-norbornene-endo-2,3-dicarboxylic acid

A 2D-MOF, namely [Cd(NDA)H₂O]·0.5H₂O (1), was synthesized by the solvothermal reaction of norbornene-based ligand, cis-5-norbornene-endo-2,3-dicarboxylic acid (NDA) and Cd(NO₃)₂·6H₂O in N,N-dimethylformamide (DMF) and water. 2D structure was constructed by the coordination of distorted octahedral Cd(II) centers and carboxylic group of the NDA ligand. The Cd(II) centers are connected with the NDA ligand to form a 2D network with hcb (6,3) network topology. Photoluminescence measurements in solid-state indicated that 1 displayed blue-light emission with the excitation wavelength at 365 nm and the CIE diagram locates the emission in the blue-light region with chromaticity coordinates at (0.17, 0.14). DFT and TD-DFT calculations reveal that this blue-light emission arises from ligand-to-metal charge transfer (LMCT) process, where the HOMO is localized on the organic linker and the LUMO on the Cd(II) center, highlighting the key role of cadmium in tuning the photophysical properties. These results demonstrate that 1 possesses suitable characteristics as a standalone blue-light emitting material for future optoelectronic applications.