Core-shell MOF@COFs with hierarchical pores for synergistic extraction of Cl/Br-substituted organic pollutants

Functionalized metal organic framework (MOF) and covalent organic framework (COF) composites (MOF@COFs) with complementary advantages, hierarchical pores, pre-designable and tunable structures, are expected for remarkable adsorption of organic pollutants, yet to be explored. Herein, a kind of MOF@COF composite was synthesized by combining the parent MIL-68(In) and COF-V (10 %-MIL-68@COF-V), characterized with well-retained crystallinity and hierarchical pores. The parent materials and as-prepared MIL-68@COF-Vs were further fabricated as solid phase microextraction (SPME) coatings to study their extraction performance for Cl/Br-substituted organic pollutants. The 10 %-MIL-68@COF-V coated fiber exhibited the most outstanding enrichment performance for Cl/Br-substituted organic pollutants mainly due to the synthetic advantages, which was 1.1-196.5 times superior than that of the commercial PDMS coating. By combining it with gas chromatography-mass spectrometry (GC-MS), an ultrasensitive method was established, exhibiting wide linear ranges (1-5000 ng L^-1), low LODs (0.17-0.29 ng L^-1), and good reproducibility. The trace Cl/Br-substituted organic pollutants in marine water samples were successfully detected, verifying the practicability of the developed method in environmental monitoring.