[Recent advances in research on sample pretreatment methods based on supramolecular-derived porous organic polymers]

Porous organic polymers (POPs) are a class of materials composed of organic building blocks usually consisting of the elements C, H, O, N, and B and other light elements connected by covalent bonds. Owing to the diversity of synthesis methods in organic chemistry, POPs can be prepared by Suzuki coupling, Sonogashira-Hagihara cross-coupling, Schiff-base condensation, Knoevenagel condensation, and Friedel-Crafts alkylation. POPs show great application potential in the field of sample pretreatment because of their large specific surface area, adjustable pore size, high tailorability, and easy modification. The design of new functional building blocks is an important factor in advancing the development of POPs and is key to the efficient separation and enrichment of target molecules in complex substrates. In recent years, supramolecular-derived compounds have provided new inspiration and breakthroughs in the construction of POPs on account of their excellent host-guest recognition properties, simple functionalization strategies, and adjustable topological configurations. The "cavitand-to-framework" approach, that is, the knitting of 0D macrocycles into hierarchical 2D or 3D POPs using suitable linkers, and extension of the research scope of supramolecular chemistry from discrete cavities to rigidly layered porous organic frameworks can lead to significant improvements in the porosity and stability of supramolecular-derived compounds. They can also provide an effective means to expand the structural diversity of POPs and generate layered structures with high porosity. This review summarizes the preparation strategies and structural characteristics of supramolecular-derived POPs with different structures, such as crown ether-based POPs, cyclodextrin-based POPs, and calixarene-based POPs. The promising applications of these materials in sample pretreatment focusing on food analysis and environmental monitoring, including epoxides, organic dyes, heavy metals, algatoxins, halogens, and antibiotic drugs, are then summarized. Next, the extraction mechanisms mainly attributed to host-guest recognition, π-π stacking, and hydrogen-bonding and electrostatic interactions between the supramolecular structures and analytes are described. The key role and potential advantages of the different preparation strategies and structural characteristics of these POPs in sample pretreatment are also discussed. Finally, the future prospects and remaining challenges of supramolecular-derived POPs are proposed. Supramolecular-derived POPs can not only achieve the rapid and selective extraction of target analytes during sample pretreatment but also improve the extraction effect of online solid phase extraction technologies. However, although numerous supramolecular-derived POPs have been developed, few have been applied in the field of sample pretreatment. Thus, the expansion of the application potential of more POP materials requires further exploration and research. The design and synthesis of supramolecular-derived POPs with highly selective recognition performance remains an important research direction in the field of sample pretreatment.