Development　of　a　simple,　highly　selective,　and　sensitive　analytical　method　for　phthalate　monoesters　(mPAEs)　remains　a　challenge　due　to　the　complexity　of　biological　samples.　To　address　this　issue,　Cu2+　immobilized　magnetic　covalent　organic　frameworks　(Fe3O4@TtDt@Cu2+　composites)　with　core-shell　structures　were　prepared　to　enhance　the　enrichment　efficiency　of　mPAEs　by　a　facile　approach　synthesis　of　COFs　shells　with　inherent　bifunctional　groups　on　Fe3O4　NPs　and　further　Cu2+　immobilization.　The　composites　exhibit　high　specific　surface　area　(348.1　m2　g−1),　outstanding　saturation　magnetization　(34.94　emu　g−1),　ordered　mesoporous　structure,　Cu2+　immobilization,　and　excellent　thermal　stability.　Accordingly,　a　magnetic　solid-phase　extraction　(MSPE)　pretreatment　technique　based　on　Cu2+　immobilized　COF　composites　combined　with　high-performance　liquid　chromatography-tandem　mass　spectrometry　(HPLC-MS/MS)　was　established,　and　key　parameters　including　the　adsorbent　amount,　adsorption　time,　elution　solvent,　etc.　were　examined　in　detail.　The　developed　analytical　method　showed　wide　linear　ranges　(10–8000　ng　L−1),　low　limit　of　detections　(LODs,　2–10　ng　L−1),　and　good　correlation　coefficients　(R2　≥　0.9904)　for　the　five　mPAEs.　Furthermore,　the　analytical　method　was　also　successfully　applied　to　the　highly　sensitive　detection　of　metabolite　mPAEs　in　mouse　plasma　samples,　indicating　the　promising　application　of　the　Fe3O4@TtDt@Cu2+　composites　as　a　quick　and　efficient　adsorbent　in　the　sample　pretreatment.　©　2022　Elsevier　B.V.