Preparation and Room Temperature Phosphorescent Properties of Cd(II) Homo- and Zn(II)Cd(II) Heterometallic Coordination Polymers Microstructures

The preparation of coordination polymers with good room temperature phosphorescence is the focus of current research. In this paper, zinc and cadmium were used as metal ions and 2,3-pyridinedicarboxylic acid (H₂L = 2,3-pyridinedicarboxylic acid) was used as organic ligands to successfully synthesize Cd (II) homometallic [CdL]·H₂O and Zn(II)Cd(II) heterometallic [ZnCdL₂]·DMF·5H₂O coordination polymers microstructures. In addition, morphology, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), elemental analyses, thermogravimetric analysis (TGA) and their luminescence properties were studied. Cd-CP is a micron-sized spherical structure, while Zn/Cd-CP is a flower-like structure formed by the accumulation of sheets. The results show that Cd(II) homo- and Zn(II)Cd(II) heterometallic coordination polymers have quantum yields of 10.05% and 8.54%, respectively. It is worth noting that the lifetime of Cd-CP is 124.62 ms, while the lifetime of Zn/Cd-CP is significantly extended to 363.09 ms after doping with metal ion Zn²⁺. The phosphorescent lifetime of coordination polymers was improved by the heterometallic doping strategy, which provided a new idea and method for the preparation of coordination polymers with long-lived room temperature phosphorescent properties. In addition, the two coordination polymers exhibited blue and cyan fluorescence at 365 nm UV light, respectively, and a green afterglow of about 2 s could be observed with the naked eye when the UV lamp was turned off.