Insights into the Imprinting and Rebinding Performance of Molecularly Imprinted Hybrids for Bisphenol A and Bisphenol F

Abstract

This study investigates the factors influencing the imprinting performance of molecularly imprinted hybrids (MIHs) with various template/monomer associations and their corresponding adsorption ability for three bisphenol analogues, bisphenol A (BPA), 2,2′-bisphenol F (2BPF), and 4,4′-bisphenol F (4BPF). Styrene (St) and methacrylic acid (MAA) were selected as the primary functional monomers for template complexation. Compared with hydrophilic MAA monomers, hydrophobic St monomers were more favorable for BPA imprinting, despite the lower binding energy of π–π interactions compared to hydrogen bonds. However, St monomers were unsuitable for 4BPF imprinting, while 2BPF exhibited limited complexation with MAA monomers. Among the bisphenols, BPA demonstrated the strongest imprinting capability, leading MIHs to exhibit the highest imprinting factor (IF = 14–18), adsorption capacity (Q_max = 43.7–47.6 mg/g), binding affinity (K_L = 4.52–6.74 L/mg, ΔH_ads^° = −35.2 to −38.9 kJ/mol, and ΔS_ads^° = −40.5 to −50.6 J mol^–1 K^–1), and selectivity over 2BPF and 4BPF (2.0–3.5). In contrast, 2BPF- and 4BPF-imprinted hybrids exhibited significantly lower adsorption capacities (Q_max = 19.4–26.7 mg/g) and binding affinities (K_L = 1.22–4.35 L/mg) for their respective templates. In competitive adsorption systems, bisphenol rebinding followed the trend BPA > 2BPF > 4BPF, regardless of which template was used for imprinting. Based on NMR analysis, the superior structure-directing and competitive rebinding abilities of BPA are attributed to the restricted rotation of its two phenyl groups, p-OH groups, and additional -CH₃ groups on the bridged carbon, which enhance π–π stacking, H-bond, CH−π, and hydrophobic interactions within the imprinted cavities. In contrast, the o-OH groups of 2BPF and the rotational phenyl groups of 4BPF hinder their imprinting and rebinding via H-bond and π–π interactions, respectively.