Borax as a Versatile Multifunctional Agent for Next-Generation Molecularly Imprinted Polymers

Abstract

Molecularly imprinted polymers (MIPs) are synthetic receptors for selective molecular recognition in biosensing and separations. Yet, their efficacy is limited by conventional organic solvent-based template removal, which degrades recognition sites, reduces adsorption capacity, compromises reusability, and undermines analytical performance, while also posing environmental issues. Herein, we introduce borax as an efficient, multifunctional agent that simultaneously enables mild aqueous template removal, suppresses nonspecific adsorption, enhances optical detection, and thus improves analytical performance. Through reversible coordination between borate species and ortho-dihydroxy or polyol groups, borax provides a universal, eco-friendly, and cost-effective purification pathway, applicable to diverse templates, including dihydroxybenzenes, polyphenols, glycosides, and sugars. Physicochemical characterizations, including Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, and scanning and transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy, demonstrate the nanoscale morphology, enhanced porosity, and preserved polymer integrity, enabling high-performance surface recognition. The resulting MIPs treated with borax demonstrate adsorption capacities exceeding 50 mg/g, imprinting factors of 67, and up to 2-fold higher selectivity compared with MIPs treated with methanol/acetic acid. Nonimprinted polymers show negligible adsorption, confirming suppressed nonspecific adsorption. The adsorption performance demonstrates rapid equilibrium within 15 min and efficient recyclability of 84% after five cycles. Besides, the MIPs were applied as sorbents in solid-phase extraction. In this system, borax acted as an efficient eluent and formed a stable boronate complex with the analyte, enabling direct UV–Vis detection at 310 nm with enhanced sensitivity compared to the noncomplexed analyte. This dual function resulted in excellent linearity (R2 > 0.999), high recoveries (95.5–100.3%), and low detection limits (0.05–0.09 μg/mL). Collectively, these multifunctional roles position borax as an efficient and sustainable enabler of next-generation MIPs and provide an improved benchmark for high-fidelity molecular recognition.