Synergistic adsorption-photocatalysis effect of α-Fe2O3-loaded acyl chloride-covalent organic framework (AC-COF) @MIL-101 porous composites for boosted tetracycline removal

Abstract

The tendency of small-sized covalent organic framework (COF) nanoparticles to easily agglomerate, and the propensity of photo-generated carriers in α-Fe2O3 to recombine pose challenges in the efficient removal of tetracycline (TC) through adsorption-photocatalysis synergy. This study addresses these challenges by introducing MIL-101, known for its excellent chemical stability and large specific surface area. The amino functional group facilitates the in-situ growth of acyl chloride-covalent organic framework (AC-COF) on the surface of MIL-101, resulting in the fabrication of AC-COF@MIL-101 with a core-shell structure. Loading α-Fe2O3 through structural regulation leads to the preparation of the final α-Fe2O3/AC-COF@MIL-101 ternary nanocomposite. In α-Fe2O3/AC-COF@MIL-101 composites, the high surface energy of AC-COF is mitigated by the strong chemical energy of NC-N, reducing AC-COF aggregation and decreasing the recombination rate of photogenerated carriers in α-Fe2O3. The heterojunction structure between AC-COF@MIL-101 and α-Fe2O3 enhances the degradation of TC, attributed to the synergistic effect of adsorption and photocatalysis. Experimental results demonstrate that α-Fe2O3/AC-COF@MIL-101 has a maximum adsorption capacity of 135.14 mg/g, achieving a 100% TC removal rate within 30 min. Compared to AC-COF, MIL-101, and α-Fe2O3, α-Fe2O3/AC-COF@MIL-101 exhibits higher adsorption capacity and photocatalytic activity. Specifically, its adsorption capacity is 2.1 times that of AC-COF, 1.8 times that of MIL-101, and 10.6 times that of α-Fe2O3. Additionally, its degradation ability is 8.6 times that of α-Fe2O3. The adsorption of TC by α-Fe2O3/AC-COF@MIL-101 occurs through monolayer chemical adsorption, and the process is exothermic. The main active species involved in the photocatalytic degradation process are h+ and ·OH. This study introduces a new ternary composite multifunctional material with high adsorption and photocatalytic performance for TC, offering a potential strategy for enhancing the synergistically adsorption-photocatalytic effect in ternary composite systems.