Porous covalent organic framework nanofibrous membrane for excellent enrichment and ultra-high sensitivity detection of trace organochlorine pesticides in water.

Developing adsorbents with high performance and long service life for effective extracting the trace organochlorine pesticides (OCPs) from real water is attracting numerous attentions. Herein, a self-standing covalent organic framework (COF-TpPa) membrane with fiber morphology was successfully synthesized by using electrospun nanofiber membranes as template and employed as solid-phase microextraction (SPME) coating for ultra-high sensitivity extraction and analysis of trace OCPs in water. The as-synthesized COF-TpPa membrane exhibited a high specific surface area (800.83 m2 g-1), stable nanofibrous structure, and excellent chemical and thermal stability. Based on the COF-TpPa membrane, a new SPME analytical method in conjunction with gas chromatography-mass spectrometry (GC-MS) was established. This proposed method possessed favorable linearity in concentration of 0.05-2000 ng L-1, high sensitivity with enrichment factors ranging from 2175 to 5846, low limits of detection (0.001-0.150 ng L-1), satisfactory precision (RSD < 10 %), and excellent repeatability (>150 cycles), which was better than most of the reported works. Additionally, the density functional theory (DFT) calculations and XPS results demonstrated that the outstanding enrichment performance of the COF-TpPa membrane was owing to synergistic effect of π-π stacking effects, high specific surface area and hydrogen bonding. This work will expect to extend the applications of COF membrane to captures trace organic pollutants in complex environmental water, as well as offer a multiscale interpretation for the design of effective adsorbents.