Molecularly imprinted polymers based on zeolite imidazolate framework-8 for selective removal of 2,4-dichlorophenoxyacetic acid

Novel molecularly imprinted polymers (MIPs) based on zeolite imidazolate framework-8 (ZIF-8) stabilized Pickering emulsions polymerization were successfully prepared for the selective identification and separation of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solutions. Experimentally, ZIF-8 of particle size of about 100 nm was successfully synthesized, which can be used as a stabilizer in Pickering emulsion. And then, with 2,4-D as the template monomer, 4-vinylpyridine (4-VP) as the functional monomer, the hollow spherical polymer microspheres were formed via Pickering emulsions polymerization. At last, after the removal of ZIF-8 and template, MIPs were obtained, which were characterized by Fourier transmission infrared (FT-IR) spectrometry and scanning electron microscopy (SEM). Through experiments, the results showed that the adsorption capacity of MIPs and NIPs had a good correlation with Langmuir isothermal model and the kinetic adsorption of MIPs was well suitable for the pseudo-second order kinetic model. The maximum adsorption capacity of MIPs was 108.10 mg/g, while that of NIPs was 28.22 mg/g. The imprinting factor (IF) was about 3.83. And the optimal adsorption equilibrium time was 60 min. The selective and regeneration adsorption experiments showed that MIPs had a high specific selectivity and stability. Also, MIPs revealed good selectivity for 2,4-D in complex water samples. On the basis, it could be proved that ZIF-8 is an excellent alternate for the traditional stabilizers and sacrificial materials, providing a new idea for separation and analysis of harmful substances in water environment.