[Research progress of magnetic microporous organic networks in magnetic solid-phase extraction]

Recently， magnetic microporous organic networks （MMONs） have emerged as a novel class of adsorbents in magnetic solid-phase extraction （MSPE）. By integrating the unique properties of microporous organic networks （MONs） and magnetic nanoparticles， MMONs exhibit advantages such as designable structures， facile synthesis， diverse architectures， high specific surface area， and excellent stability， garnering widespread attention in the field of sample pretreatment. The current strategies for preparing MMONs mainly include in-situ growth， post-synthetic modification （PSM）， and composite preparation. Among these， the in-situ growth method can be further categorized into direct in-situ growth， indirect in-situ growth， and co-doping methods. The direct in-situ growth method is straightforward to operate， enabling the construction of MMONs with well-defined core-shell structures. It also allows flexible control over the functionality and shell thickness of MMONs by adjusting the type and concentration of monomers， making it the most commonly used preparation method for MMONs. In contrast， the indirect in-situ growth method involves the introduction of an intermediate bridging layer， which complicates the synthesis process. However， the intermediate coating layer and the MONs shell can work synergistically to enhance the extraction efficiency of MMONs for targets. Although PSM requires additional reaction steps and poses challenges in controlling the modification rate and distribution of functional groups， it increases the variety and quantity of modifying groups and molecules， thereby expanding the application range of MMONs in MSPE. Furthermore， MMON composites can integrate the respective advantages of both MMONs and polymers， further broadening the applicability of MMONs. Therefore， each of the three methods mentioned above has its own advantages and disadvantages. Researchers can select the appropriate synthesis method based on the specific requirements of MSPE to prepare the desired MMONs. This review also provides a detailed discussion on the applications of MMONs in the MSPE of various organic pollutants， including pharmaceuticals， pesticides， endocrine-disrupting chemicals， mycotoxins， food additives， and per- and polyfluoroalkyl substances， and elucidates the extraction mechanisms （e.g. hydrophobic interaction， π-π stacking， electrostatic attraction， hydrogen-bonding interaction， ion pair interaction， fluorine-fluorine interaction， and π-CF interaction） between MMONs and analytes. In response to the current challenges of MMONs， future research should focus on the following areas： （1） Designing and expanding low-cost functional monomers to enrich the variety and quantity of existing functional monomers， providing other effective PSM methods for synthesizing functionalized MMONs， and introducing other functional composites to prepare MMON composites. （2） Developing target-oriented structural design or functionalization strategies to construct functionalized MMONs， with the aim of improving their selectivity toward specific targets. （3） Advancing other advanced characterization and mechanism investigation techniques to understand the extraction mechanisms of MMONs and guide their structural design or functionalization. In summary， this review aims to deepen the understanding of MMONs-based MSPE methods in the enrichment and detection of various organic pollutants， while offering guidance for the synthesis and application of MMONs.