Interfacial permeation preparation of ZIF-8 in reactive deep eutectic for efficient adsorption and selective removal of Congo red

Abstract

Metal-based deep eutectic solvents (MDES) were used as reactive DESs and structure directing agents to control the morphology and oriented growth of ZIF-8. A series of ZIF-8-DESs were prepared in three MDESs (ZnCl2-urea, ZnCl2-1,3-dimethylurea and ZnCl2-tetramethyl urea) by the interfacial synthesis and two-phase permeation. The results showed that MDES acts as multi roles to affect the morphology and adsorption performance of ZIF-8-DES. The growth mechanism of ZIF-8-DES was also proposed. ZIF-8-DES could effectively adsorb anionic Congo red with 99.98 % removal efficiency, 2454 mg·g−1 adsorption capacity and a wide pH tolerance. ZIF-8-DES possesses excellent selectivity for Congo red in the presence of methyl orange and outstanding reusability as compared with pristine ZIF-8 and most reported adsorbents. The thermodynamics and adsorption kinetics was well described by a Langmuir model and pseudo-second-order model, respectively. The adsorption mechanism including π-π interaction and hydrogen bonding interactions was proposed. This work provided a facile synthesis route for MOFs with different morphologies and surface properties as well as novel insights into the design of selective absorbent for organic dyes.