Fig. 2

Phase transition and CO₂ diffusion in ZIF-7. a In situ SXRD data of ZIF-7 at T = 195 K, p(CO₂) = 0–41 kPa. λ = 0.82634(1) Å. At 0–23 kPa, the diffraction pattern corresponds to ZIF-7-II. Above 30 kPa, the diffraction pattern of ZIF-7-I dominates. b The Q dependence of the CO₂ transport diffusion coefficient D in ZIF-7 at a CO₂ loading of 1.3 mmol g⁻¹ and T = 298 K, fitted by a 4th-order polynomial function. Error bars are calculated using Supplementary Equation 6. D_t: transport diffusivity. D_t = D(0). D_s: self-diffusivity. D_t = D_s(∂ lnp/∂ lnc). p is CO₂ pressure in kPa and c is CO₂ uptake at p in mmol g⁻¹. See Supplementary Discussion for detailed analysis. c The Q dependence of the CO₂ transport diffusion coefficient D in ZIF-7 at a CO₂ loading of 1.3 mmol g⁻¹ and T = 225 K, fitted by a linear function. Error bars are calculated using Supplementary Equation 6