Development of a chromium-based metal–organic framework, MIL-88B(Cr), modified with deep eutectic solvents for the efficient, simultaneous removal of bisphenol A and bisphenol S

Abstract

The efficient removal of bisphenol pollutants is essential for the protection of the human health and the ecological environment. In this work, a novel composite was successfully constructed from a chromium-based metal–organic framework, MIL-88B(Cr), with its structural stability and surface modified with green deep eutectic solvents (DESs) derived from methacrylatoethyl trimethyl ammonium chloride, acrylamide, and caffeic acid. The application of DESs introduced functional groups that enhanced the adsorption performance via hydrogen bonding and electrostatic interactions, which further realized the efficient, simultaneous removal of bisphenol A and bisphenol S (BPA and BPS). This composite, namely, DES@MIL-88B(Cr), exhibited an optimum adsorption performance towards BPS when the dosages of DES, MIL-88B(Cr), and H₂O were 0.8 mL, 0.20 g, and 30 mL, respectively. The adsorption capacities of DES@MIL-88B(Cr) for BPA and BPS reached 49.05 mg g⁻¹ and 91.40 mg g⁻¹, which were 3.12 and 16.60 times higher than those of MIL-88B(Cr), respectively. Moreover, DES@MIL-88B(Cr) achieved adsorption equilibrium within 10 min and 5 min for BPA and BPS, respectively. The pseudo-first-order kinetic model and the Langmuir isotherm model fitted best among all other adsorption models for both BPA and BPS. Thermodynamic analysis revealed that the adsorption processes occurred spontaneously and exothermically. The adsorption mechanisms were mainly attributed to hydrogen bonding, electrostatic interactions, and π–π conjugation. DES@MIL-88B(Cr) effectively removed BPA and BPS from 9 environmental water and plastic samples and achieved recoveries of 92.82%–114.43% for BPA and BPS. Furthermore, DES@MIL-88B(Cr) maintained over 96% efficiency after 10 regeneration cycles. This work offers new perspectives on the potential application of DES-modified MOFs as green, high-performance adsorbents and provides a sustainable strategy for the removal of emerging contaminants.