Progress in functional covalent organic frameworks as advanced materials for sample pretreatment

Covalent organic frameworks (COFs) represent an emerging class of porous crystalline materials with immense potential as advanced materials for sample pretreatment. Their distinctive characteristics, including large specific surface area, adjustable pore structures, robust chemical stability, and abundant active sites, render them a reliable platform for efficiently extracting analytes, thereby opening avenues for innovative applications in analytical chemistry. This review focuses on recent research progress in the utilization of functional COFs for the preconcentration of contaminants, including organic pollutants (such as drugs, pesticides, and dyes) and heavy metal ions. COFs featuring diverse functional groups, such as carboxyl, sulfonyl, hydroxyl, amino, nitro and halogen moieties and their integration with advanced sample pretreatment techniques are discussed. The review begins by examining two primary strategies for functionalizing COF: "bottom-up" and "post-synthetic modification". Subsequently, the interaction mechanisms and analytical performances of methods based on functionalized COFs are critically analyzed, emphasizing their extraction efficiency and selectivity. Finally, the technical merits of functional COFs as high-performance adsorbents in sample pretreatment are highlighted, while addressing current challenges and outlining future research directions. This review aims to provide a comprehensive reference for the rational design and practical applications of functionalized COFs in advanced sample pretreatment workflows.