Composite SPE Paper Membrane Based on the Functional Superstructure of Metal–Organic Frameworks and Ionic Liquids for Detection of Tetracycline-like Antibiotics

Composite adsorbents based on metal-organic frameworks (MOFs) are excellent candidates for solid-phase extraction (SPE) due to their diverse chemical functionality and multilevel porosity. MOF superstructures based on self-assembly at room temperature (RT) could have less energy consumption and easier manipulation due to the larger complex geometry. The π-π stacking of the benzene ring could not only enhance the interaction toward hydrophobic or plane-structured targets but also be expected to promote the formation of the MOF superstructure. In this work, in the established RT self-assembly synthesis system, several factors were investigated to see how to obtain functional MOF superstructures with a regular geometry, among which the number of benzene rings in the ligand was mainly tested for its impact on self-assembly and adsorption capacity. By means of adsorption experiments and computational fluid dynamics (CFD) simulation, the relationship between structure and activity (SARs) was further explored. Interestingly, the MOF unit with the lowest specific surface area performed the best in adsorption. Then, the selected functional MOF superstructure and ionic liquid were used to produce the composite paper membrane facilely applied in the SPE device. After optimization of the preparation conditions and operation parameters, the established SPE-HPLC-UV method could selectively analyze tetracycline-like antibiotics in the range of 16.6-833.3 ng/g (ppb) in a meat sample. This work provided an RT synthesis method to produce a microsize MOF superstructure, with experimental and theoretical insights into the SARs, which could be expanded in the design of other MOF-based SPE composite membranes toward one group of analogues.