Bio-inspired chitosan aerogel decorated with MOF-on-COF heterostructure hybrid as recyclable scavenger of herbicides in water

Concerns about water contamination caused by pesticide residues have driven attempts to exploit efficient adsorbents with high adsorption, easy recycling and reuse. Herein, inspired by the accumulation and toxic mechanism of herbicides in corals, a separation-free shapable adsorbent was developed by enveloping a MOF-on-COF hybrid into chitosan (CS) aerogel to remove 2, 4-dichlorphenoxyacetic acid (2, 4-D) and glyphosate (GLP) herbicides. The hybrid which prepared via in situ loading of Zr based metal organic framework (UiO-67) onto a flower-like covalent-organic framework (COF) can function as anchoring tentacles to capture herbicides and improve adsorption. Additionally, the porous structure of CS aerogel can mimic the three-dimensional structure of corals, allowing for the rapid delivery of herbicides from aqueous solution to the aerogel interior. Benefiting from these appealing advantages, the adsorbent displayed excellent removal performance with rapid adsorption equilibrium (2, 4-D: 60 min; GLP: 120 min) and high adsorption capacities (2, 4-D: 615.12 mg/g; GLP: 675.48 mg/g). Moreover, the aerogel possessed satisfactory recyclability after five successive cycles. In addition to hydrogen-bonding and electrostatic interactions, π-π interaction and chemical adsorption between phosphate moieties of GLP and Zr-O clusters was also involved in 2, 4-D and GLP adsorption. Accordingly, the tactics presented a viable option for designing novel adsorbents with porous structures, abundant function groups and ease-of-reusability to remove pollutants.