Adsorption and diffusion of carbon dioxide on the metal-organic framework CuBTB

- Temperature-dependent Toth equation provides a good fit to CO2 isotherms on CuBTB.
- The maximum adsorption capacity at 300 K is 2.08 mmol/g.
- The diffusivity of CO2 on CuBTB is around 1.57-9.85 × 10−12 m2/s from 280 K to 350 K.
- The diffusion time constant (De/r2) is in the range of 24.6-3.93 × 10−3 s−1.
- A dual linear-driving force (LDF) model provides better fit to kinetic data than a micropore diffusion model.

The metal-organic framework (MOF) CuBTB was synthesized and used to study adsorption and diffusion of carbon dioxide (CO2) in the crystal. Experimentally measured CO2 adsorption isotherms can be successfully fitted using the Toth adsorption model. The maximum adsorption capacity at 300 K and 350 K is 2.08 and 1.08 mmol/g, respectively. The isosteric heat of adsorption of CO2 on CuBTB is about 26.4 kJ/mol. The intracrystalline diffusivity of CO2 on CuBTB, obtained with a one-dimensional micropore diffusion model, is in the range of 1.57-9.85 × 10−12 m2/s from 280 K to 350 K, while the diffusion time constant (De/r2) is in the range of 24.6-3.93 × 10−3 s−1, which is higher than some zeolites. A dual linear-driving force (LDF) model used to estimate the kinetic constants provides an overall better fit to the experimental data than the one-dimensional micropore diffusion model.