Fig. 7. SEM images of ZIF-8 samples: (a) mixing method (MeOH), (b) solvothermal method (MeOH), (c) ultrasonic method (MeOH), (d) mixing method (DMF), (e) solvothermal method (DMF), (f) ultrasonic method (DMF), (g) mixing method (water), (h) solvothermal method (water) and (i) ultrasonic method (water).