Convenient preparation of spongy chitosan composite of metal-organic framework with high adsorption for dyes or metal ions

• A scalable synthesis method is developed for fabricating a chitosan/MIL-68(Al) composite aerogel. • The sponge-like adsorbent removes diverse pollutants under mild conditions without additives. • Methyl orange adsorption reaches equilibrium within 10 minutes. • The aerogel achieves a high adsorption capacity of 496.72 mg/g and can be effectively reused This study developed a composite aerogel by incorporating a typical metal-organic framework (MIL-68(Al)) into a low-cost chitosan matrix through cross-linking and freeze-drying, aiming to facilitate efficient pollutant removal. An environmentally friendly chitosan/MIL-68(Al) composite aerogel with a mass ratio of 10:1 (denoted as CS 10 /MIL-68(Al), chitosan (CS)) was synthesized under mild conditions, exhibiting a low density of 0.013 g/cm 3 . The resulting sponge-like adsorbent overcomes the limitations of powdered MOFs, such as poor recyclability and cumbersome handling, while maintaining structural stability before and after adsorption and allowing easy retrieval from solution with forceps. The material was comprehensively characterized by FT-IR, XRD, XPS, and SEM. Adsorption experiments showed that methyl orange (MO) reached equilibrium within 10 minutes, with a maximum adsorption capacity of 496.72 mg/g. The aerogel retained over 50% removal efficiency after four regeneration cycles. Density functional theory (DFT) calculations were employed to analyze adsorption energy profiles and identify the optimal configuration between CS 10 /MIL-68(Al) and key functional sites of MO. Further tests confirmed its effectiveness toward various pollutants and metal ions. Mechanistic studies indicated that the rapid adsorption process is governed by electrostatic attraction, π–π stacking, hydrogen bonding, and coordination interactions. This work provides a simple and efficient synthesis route for a robust MOF-based aerogel adsorbent, demonstrating strong potential for practical application in the treatment of wastewater contaminated with organic dyes and other pollutants.