Heteroatoms-rich hyper-cross-linked polymers for rapid adsorption of chlortetracycline

Conventional adsorbents often suffer from limited adsorption kinetics and capacity for chlortetracycline (CTC). Here, two dual maleimide-based hyper-crosslinked polymers (HCP-BMI-1 and HCP-BMI-2) via one-step Friedel-Crafts alkylation were synthesized using bismaleimide (containing N/O functionalities) as the monomer and DCX (1,4-bis(chloromethyl)benzene) or BCMBP (4,4′-bis(chloromethyl)-1,1′-biphenyl) as cross-linkers. The choice of cross-linker significantly influenced polymer properties, including morphology, chemical composition, and pore structure. Notably, HCP-BMI-2 exhibited a hierarchical structure formed by the spontaneous aggregation of nanoparticles in non-uniform arrangements. Compared to HCP-BMI-1, HCP-BMI-2 displayed superior physicochemical properties: a higher BET surface area (938 m²/g), enhanced pore volume (0.758 cm³/g, 80 % meso/macropores), and increased heteroatom content (N: 2.96 %, O: 10.02 %). These characteristics contributed to its enhanced CTC adsorption performance. Owing to its excellent hydrophilicity and heteroatom-rich framework, HCP-BMI-2 achieved rapid adsorption (495 mg/g within 30 min), outperforming most reported adsorbents in both kinetics and maximum capacity. Mechanistic studies revealed that CTC uptake was governed by hydrogen bonding, electrostatic interactions, and π-π stacking. Moreover, HCP-BMI-2 retained high adsorption efficiency after 10 regeneration cycles, demonstrating robust reusability. This work provides a strategic approach to designing high-performance adsorbents for efficient CTC removal.