Zwitterionic hybrid aerobeads of binary metal organic frameworks and cellulose nanofibers for removal anionic pollutants

Abstract

Different adsorbents have been applied to remove various anionic pollutants in water treatment processes. However, the development of economic, sustainable, and high-performance adsorbents is still a challenge. Herein, we introduce a new strategy to produce highly porous (98.96%), very low density (0.015 g/cm3), and cost-effective spherical and nanostructured hybrid aerogels, termed aerobeads, from cellulose nanofibers (CNF) and metal-organic frameworks (MOFs). The zwitterionic MOFs@CNF aerobeads (with 10–50 wt% MOF loading) were synthesized via simple dropping of a cross-linked hydrogel containing CNF and a binary mixture of anionic and cationic MOFs in liquid nitrogen, followed by freeze-drying. The flexible aerobeads (diameter of 2–3 mm) with hierarchical porous structure demonstrated an outstanding adsorption capacity toward both diclofenac (121.20 mg/g) and methyl orange (49.21 mg/g). Moreover, the aerobeads were easily collected after use from the solution without any complicated separation methods or the formation of secondary pollutants.