Porous Imprinted Microspheres with Covalent Organic Framework-Based, Precisely Designed Sites for the Specific Adsorption of Flavonoids

Abstract

The application of microsphere molecularly imprinted materials for the targeted extraction and purification of flavonoids derived from agricultural waste has emerged as a prominent area of investigation. An innovative boronate affinity imprinted microsphere (MC-CD@BA-MIP) was successfully synthesized using the Pickering emulsion interfacial assembly strategy for the selective separation of naringin (NRG). The double-bond functionalized covalent organic framework (COF)-based microspheres were synthesized through Schiff–base reaction and secondary interfacial emulsion polymerization. Then, the synthetic mono-(6-mercapto-6-deoxy)-β-cyclodextrin (SH-β-CD) was grafted onto the surface of the microspheres (MC) using click chemistry. The 1-allylpyridine-3-boronic acid (APBA) as a functional monomer was grafted onto the initiator (ABIB) through atom transfer radical polymerization (ATRP). Ultimately, the synthesized boronic acid-imprinted ABIB-BA-MIPs were immobilized onto the COFs microsphere surface through host–guest interactions. As expected, under neutral conditions, the MC-CD@BA-MIPs still exhibited a significant adsorption capacity (38.78 μmol g−1 at 308 K) for NRG. The regenerated MC-CD@BA-MIPs maintained 92.56% of their initial adsorption capacity through six consecutive cycles.