Surface engineering of 3D covalent organic frameworks via crystalline modulation for enhanced profiling of...

Surface engineering of covalent organic frameworks (COFs) represents a highly promising strategy for achieving superior capture capacity towards environmental trace pollutants. Herein, the three-dimensional covalent organic frameworks (3D-COFs) with tunable crystallinity were synthesized and optimized via a simple solvent ratio adjustment, demonstrating an exceptional capture capacity of polychlorinated biphenyls (PCBs). By adjusting the ratio of solvents (1,4-dioxane and toluene), a functional 3D COF (dia-c5 TPA-TAM-COF) was discovered, providing an ideal approach to transform an amorphous compound into a functional platform with a significant increase in crystallinity, surface area and pore volume for PCBs capture. The adsorption features and analytical performance of PCBs were evaluated, and a good performance was achieved with high enrichment factors as 6973 ∼ 11,015. Optimization of solid phase microextraction (SPME) using the dia-c5 TPA-TAM-COF as the coating was investigated, and the method was verified for sensitive quantification of PCBs by using GC-MS, achieving the sensitive limits of detection (LODs) of 0.028 ∼ 0.0263 ng/L. Good reproducibility and robustness of the analytical performance of PCBs using dis-c5 was achieved, with the RSDs of intra-day (n = 3), inter-day (n = 6) and fiber-to-fiber (n = 3) of 0.7 ∼ 4.7 %, 1.8 ∼ 4.6 % and 2.0 ∼ 3.9 % respectively. The recoveries of PCBs in the soil fortified samples were obtained as 85.3 ∼ 101.9 % and 86.3 ∼ 108.8 %, respectively, as well as high thermal stability and long lifetime (keep on going more than 150 cycles). This study demonstrates that a simple protocol of adjusting the solvent content was capable of tailoring high crystallinity and suitable interpenetration degree of TPA-TAM-COFs for high performance target capture of PCBs in environmental soils.