Abstract: As a clean and efficient energy, nuclear energy is widely used in various fields of power, medical and breeding. Radioactive waste liquids are produced in nuclear facilities during normal operation or in the event of an accident. Among them, ⁶⁰Co not only has long-term radioactivity, but also has chemical toxicity. Once discharged into the environment with the waste liquid, it will cause continuous radioactive pollution to the ecology. Therefore the development of an adsorbent with high selectivity, large adsorption capacity and fast adsorption capacity for Co(Ⅱ) is crucial for the treatment of radioactive waste liquids. In this study, ZIF-90, a metal-organic framework material, was synthesized at high temperature in DMF system, and then through post-synthesis modification, the free aldehyde group on ZIF-90 was condensed with thiosemicarbazide (TSC) in methanol solution at high temperature to further synthesize functionalized MOFs material ZIF-90-TSC. The synthesized ZIF-90 and ZIF-90-TSC were characterized by scanning electron microscopy, thermogravimetric analysis, N₂ adsorption-desorption, X-ray diffraction and Fourier transform infrared spectroscopy. The effects of initial pH, adsorption time, initial concentration of Co(Ⅱ) and temperature on the adsorption of Co(Ⅱ) on ZIF-90-TSC were also investigated. The characterization results show that the average crystal size of ZIF-90-TSC is less than 500 nm with a microporous structure, and it has good thermal stability within 280 ℃. The results of adsorption experiments show that ZIF-90-TSC has the best adsorption performance for Co(Ⅱ) in the weak alkaline environment. The adsorption equilibrium time for Co(Ⅱ) is about 80 min. The maximum adsorption capacity of ZIF-90-TSC for Co(Ⅱ) is 151.23 mg/g under the conditions of initial pH=6.70, T=303 K and initial Co(Ⅱ) concentration of 500 mg/L. The adsorption-diffusion model analysis shows that the adsorption of Co(Ⅱ) on ZIF-90-TSC is more in line with the Boyd model, revealing that the effect of liquid film diffusion on the adsorption rate is dominant in the entire adsorption process. Thermodynamics, kinetics and isotherm model analysis results show that the adsorption process of Co(Ⅱ) by ZIF-90-TSC is spontaneous and endothermic, in line with pseudo-second-order kinetic model and Langmuir isotherm model, which indicates that the adsorption process is a chemical process and occurs on the surface monolayer. ZIF-90-TSC exhibits selective adsorption of Co(Ⅱ) and Ni(Ⅱ) in multi-metal ion solution. Compared with other traditional adsorbents, ZIF-90-TSC not only has a larger adsorption capacity, but also has a shorter adsorption equilibrium time, which is beneficial for waste minimization. Therefore, ZIF-90-TSC has a certain application prospect in the adsorption treatment of Co(Ⅱ) in radioactive waste liquid.