Enhanced hydrophobicity of modified ZIF-71 metal-organic framework for biofuel purification

Abstract

Hydrophobic materials are desirable for biofuel purification applications. In this work, the atomic substitution of Cl atom with Br atom in the imidazole organic linker was carried out to produce a more hydrophobic ZIF-71, named ZIF-71(ClBr) and ZIF-71(ClBr)-SE for the material with an additional solvent exchange procedure. The physicochemical characterization revealed that ZIF-71(ClBr) and ZIF-71(ClBr)-SE are isostructural to ZIF-71, have a high surface area (769 and 969 m2/g), and are hydrophobic (126 and 130° water contact angle). As a proof of concept, D4 siloxane adsorption capacity onto ZIF-71(ClBr) and ZIF-71(ClBr)-SE was estimated (1.76 and 2.66 mg/g, respectively). Furthermore, a superior adsorption capacity was obtained when ZIF-71(ClBr)-SE was used due to its higher hydrophobic nature, and similar results were obtained with ZIF-8, used as a frame of reference. Therefore, the high surface area and the hydrophobic nature of ZIF-71(ClBr)-SE make it compelling material for biofuel purification applications.