ZIF-8 powder was synthesized based on Zhang et al. Briefly, 595.0 mg (2 mmol) of zinc nitrate hexahydrate and 656.8 mg (8 mmol) of 2-methylimidazole were dissolved separately in 40 mL of methanol each. The latter solution was rapidly added to the former solution under stirring and stirring was stopped after 1 minute. After 24 hours, white solids were separated from the dispersion by centrifugation at 10,000 rpm for 5 min, followed by washing two times with methanol and one time with isopropanol. The resultant powder was dried overnight at 60 °C.