Metal framework functionalized with nitro groups and chitosan composite adsorption of Congo red

Dye pollution is a significant global environmental issue. To address this problem, various adsorbents have been employed, but traditional adsorbents often suffer from poor reusability and limited adsorption efficiency. Metal-organic frameworks (MOFs), which have emerged in recent years, have excellent physicochemical properties, but their application in wastewater treatment is limited by their polycrystalline, powdered state. In this paper, nitro functional groups were added to MIL-88B. The specific surface area of MIL-88B-NO₂ obtained after the treatment was 660.98 m²/g, which was enhanced by 80 % compared with MIL-88B, with more excellent physicochemical properties. Subsequently, MIL-88B-NO₂ was combined with chitosan to form the MIL-88B-NO₂/CS aerogel, which addressed the problem of difficult separation of MOFs from water. The maximum adsorption amount of the aerogel for Congo Red (CR) was 878.8 mg/g. The adsorption process of CR by the adsorbent designed in this paper is consistent with the pseudo-second-order kinetic model and the Sips model, indicating that it is a complex physicochemical process. The adsorption mechanism is mainly synergistic with the effects of π-π conjugation, electrostatic attraction and hydrogen bonding. MIL-88B-NO₂/CS aerogel demonstrated excellent reusability, maintaining a CR removal rate of 80 % after five adsorption-desorption cycles, indicating its promising application in dye removal.