Metal–Organic Framework–Polymer Composite as a Highly Efficient Sorbent for Sulfonamide Adsorption and Desorption: Effect of Coordinatively Unsaturated Metal Site and Topology

In this study, we first demonstrated the effect of two types of metal–organic framework–polymer (MOF–polymer) monoliths on in-tube solid-phase microextraction (IT-SPME) of sulfonamides. Sulfonamides were successfully adsorbed onto MIL-101­(Cr)–polymer but were difficult to elute due to these sulfonamides could interact via Lewis acid–base interaction with the presence of Cr­(III) coordinatively unsaturated metal sites (CUS). Moreover, the cage-type topology of MIL-101­(Cr) that could produce multiple pathways thus complicates the desorption of the test analytes from the sorbent. Contrastingly, MIL-53­(Al)–polymer provided weaker Al­(III) CUS, and its one-dimensional channel pore structure could provide an unhindered pathway for sulfonamides transfer during elution. After optimizing the IT-SPME condition such as MOF content, pH of sample matrix, column length, extraction flow rate, and elution volume, the calculated extraction recovery of sulfonamides in MIL-53­(Al)–polymer as analyzed by microemulsion electrokinetic chromatography (MEEKC) were in the range of 40%–90% with relative standard deviations (RSDs) below 5% and a reusability of at least 30 times