Abstract:

Bisphenol A （BPA） is an endocrine-disrupting chemical that mimics estrogen， thereby interfering with human hormonal balance and leading to reproductive abnormalities， developmental disorders， and increased risks of obesity， diabetes， and cancer. Commonly found in plastic products and food packaging materials， BPA can readily leach from packaging under thermal stress or exposure to acidic/alkaline conditions， subsequently migrating into the environment. This results in its widespread presence in surface water， groundwater， and drinking water systems. Prolonged exposure poses significant health threats， while conventional wastewater treatment processes prove inadequate for its complete removal. Therefore， developing an efficient， highly specific， and reusable material for removing BPA from water systems is of substantial practical significance. Molecularly imprinted polymers （MIPs） have emerged as promising candidates for targeted pollutant removal due to their artificially created recognition sites that exhibit both structural and functional complementarity to template molecules. The unique advantages of MIPs， including their exceptional specificity， chemical stability， and reusability， make them particularly suitable for environmental applications. To address the challenge of BPA contamination in water systems， we developed a novel cobalt-nickel bimetallic metal-organic framework-based molecularly imprinted polymer （CoNi-MOF-MIPs） through an innovative surface imprinting approach. The fabrication process involved multiple carefully controlled steps. Initially， a crystalline CoNi-MOF substrate was synthesized as the supporting matrix， providing high surface area and structural stability. Dopamine hydrochloride （DA） was then employed as the functional monomer， which underwent self-polymerization under weakly alkaline conditions to form a polydopamine （PDA） coating while simultaneously immobilizing BPA template molecules through synergistic hydrogen bonding and π-π interactions. Subsequent template removal using an eluent created well-defined recognition cavities on the MOF surface. For comparison， non-imprinted polymers （CoNi-MOF-NIPs） were prepared following identical procedures without BPA addition. Critical synthesis parameters were systematically optimized through comprehensive experiments. The mass ratio of functional monomer to template molecule was determined to be optimal at 5∶4 （DA∶BPA）， while the polymerization duration and adsorption pH were optimized to 5 h and 4.0， respectively. Material characterization revealed crucial structural features： scanning electron microscopy （SEM） images confirmed the preservation of nanoflower-like morphology with hierarchical structures， providing abundant adsorption sites， while Fourier-transform infrared spectroscopy （FT-IR） demonstrated successful imprinting through characteristic peak shifts-notably the O-H stretching vibration migration from 3 443 cm⁻¹ to 3 752 cm⁻¹ and aromatic C=C bending transition from 1 633 cm⁻¹ to 1 457 cm⁻¹. Adsorption performance evaluation demonstrated remarkable efficiency across multiple aspects. Kinetic studies revealed rapid uptake conforming to pseudo-second-order behavior （R²=0.987 9 for CoNi-MOF-MIPs and R²=0.976 8 for CoNi-MOF-NIPs）， reaching equilibrium within 30 min and suggesting that the adsorption process was controlled by the availability of binding sites rather than diffusion limitations. Isotherm analysis showed excellent agreement with the Langmuir model， indicating monolayer adsorption on homogeneous surfaces with a maximum capacity of 39.29 mg/g and an impressive imprinting factor of 3.48. Competitive adsorption experiments against structural analogs （diphenolic acid and phenol） demonstrated exceptional selectivity， with selectivity factors of 5.07 and 7.35 respectively， confirming the material’s ability to specifically recognize BPA in complex matrices. The CoNi-MOF-MIPs maintained 93.2% of their initial adsorption capacity after six consecutive adsorption-desorption cycles， demonstrating excellent reusability. When coupled with high performance liquid chromatography （HPLC）， the developed analytical method exhibited a wide linear detection range （0.17-40 μg/mL， R²=0.997 4） and low detection limit （0.05 μg/mL）. Practical application to environmental water samples spiked at three concentration levels （10， 20， and 30 μg/mL） achieved satisfactory recoveries of 80.3%-91.7% with excellent reproducibility （relative standard deviation<1.8%）. The CoNi-MOF-MIPs material developed in this study combines the exceptional adsorption capacity of bimetallic MOFs with the molecular recognition precision of imprinted polymers. This innovative material demonstrates outstanding performance in both BPA enrichment and detection from environmental water samples， showing great promise for practical applications in water treatment and environmental monitoring.

Key words: molecularly imprinted polymers （MIPs）, bisphenol A （BPA）, high performance liquid chromatography （HPLC）, selective adsorption