Rapid and facile synthesis of micro-mesoporous ZIF-8 materials with enhanced adsorption of methylene blue

Abstract

Zeolitic imidazolate frameworks (ZIFs) have been widely applied in many research fields, such as catalysts and adsorption. To meet the needs of scale applications, the development of simple, rapid and high-yield synthesis is a great necessity. In this work, a novel and facile strategy for the rapid synthesis of micro-mesoporous ZIF-8-H at room temperature within a very short time of 16 min using inexpensive quaternary ammonium base (tetramethylammonium hydroxide pentahydrate, TMAH) as a template was proposed. Results showed that in addition to significantly shortening crystallization time, the TMAH template also induced abundant mesopores for ZIF-8-H, which can improve the adsorption rate and fully use the adsorption active sites. More importantly, the ZIF-8-H yield of the proposed strategy is 3.6 times more than that of the conventional method, which is conducive to the realization of large-scale production. Among ZIF-8-H-x-t, ZIF-8-H-0.8-16 prepared with TMAH/Zn2+ molar ratio x of 0.8 and reaction time t of 16 min exhibited the highest MB removal effectiveness of 96.3 ± 0.8%, a remarkable increase of 127% compared to ZIF-8-M prepared by conventional method (42.5 ± 0.9%). Additionally, the MB adsorption onto ZIF-8-M and ZIF-8-H-0.8-16 fitted well with the pseudo-first-order kinetics model and Langmuir isothermal model, suggesting the monolayer adsorption behavior is dominant. The ZIF-8-H-0.8-16 showed a maximum adsorption capacity of 47.90 mg/g, which is higher than that of ZIF-8-M.