Facile room-temperature synthesis of agarose-supported Cu-BTC metal-organic framework aerogel composites for enhanced adsorption of methylene blue and congo red dyes

Abstract

Organic dyes containing azo/anthropquinone groups pose severe ecological risks due to their toxicity and persistence. Therefore, in this study, covalently cross-linked agarose aerogel was used as the substrate, and the Cu-BTC metal-organic framework (Cu-MOF) was loaded via in-situ growth at room temperature to prepare a Cu-MOF @ agarose composite aerogel (Cu-MOF@AGA) adsorbent. The introduction of Cu-MOF endows Cu-MOF@AGA with more adsorption sites and a larger specific surface area (210.78 m²/g). The characteristic peaks at 2θ values of 6.6, 9.4, and 11.5 in the XRD pattern indicate the successful loading of Cu-MOF. Meanwhile, SEM images show that the 3D macroporous structure of Cu-MOF @AGA provides a rapid mass - transfer channel for pollutant molecules. FT-IR results reveal that Cu-MOF@AGA has more functional groups (such as -OH, -COOH) and active sites. The adsorption mechanism was analyzed using XPS and FT-IR, revealing that the adsorbent achieves adsorption of methylene blue (MB) and Congo red (CR) through hydrogen bonding, π-π interactions, and electrostatic interactions. Kinetic and isotherm fitting analyses demonstrated that the maximum adsorption capacities for methylene blue and Congo red reached 59.48 and 159.85 mg/g, respectively. Finally, after five cycles of adsorption experiments, the removal rates for MB and CR remained above 85 %, indicating that the adsorbent exhibits excellent reusability and promising application potential.