A carboxy-functionalized covalent organic framework COOH@COF for
efficient removal of Pb2+ and Hg2+ ions from
water has been prepared. Fourier transform infrared spectroscopy,
solid-state 13C NMR spectra, and elemental analysis indicate
that the carboxy function has been grafted to COF materials via the
click reaction. Its crystallinity remains unchanged after post-synthetic
modification, as confirmed by the powder X-ray diffraction. Scanning
electron microscopy images reveal that the COOH@COF possesses the
thorn ball structure assembled by numerous nanowires with a diameter
of 90 nm. This COOH@COF features excellent adsorption capacities for
Pb2+ (123.8) and Hg2+ (99.1 mg/g) in water.
The adsorption isotherms follow the Langmuir model, and their kinetics
adsorption fits the pseudo-second-order model. Particularly, the COOH@COF
can be recycled 20 times without loss of the adsorption capacity in
water, showing its latent potential for practical application in the
future.