Journal
CHEMICAL ENGINEERING JOURNAL
Volume 454, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2022.140154
Keywords
Pyridine-COF; Hg2+adsorption; High adsorption capacity; Density functional theory calculations
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A pyridine-based covalent organic framework (Pyridine-COF) was synthesized and demonstrated high selectivity and adsorption capacity for mercury ions. The framework showed good reusability and mainly relied on chelation for adsorption.
The high toxicity and carcinogenicity of mercury ions (Hg2+) motivates the development of efficient technologies for their removal from water. In this work, a pyridine-based covalent organic framework (Pyridine-COF) was synthesized via the Schiff base condensation reaction of 1,3,5-tris(4-aminophenyl)benzene (TAP) and 2,6-difor-mylpyridine (DFP) at room temperature. The obtained Pyridine-COF was crystalline, microporous and possessed a high specific surface area (348.5 m2 g-1). The close association of the pyridine linker and imine groups in the COF structure created an N-rich pore space that showed high selectivity towards Hg2+ ions. Adsorption exper-iments showed Pyridine-COF to have very fast Hg2+ adsorption kinetics, a high adsorption capacity for Hg2+ (719.4 mg g-1 at 293 K, 840.3 mg g-1 at 303 K, and 1000 mg g-1 at 313 K), and very good Hg2+ removal performance in the presence of other metal cations. Further, Pyridine-COF maintained a high adsorption capacity over five cycles of adsorption-desorption, confirming good reusability as an adsorbent. Mechanistic studies using X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed that the adsorption of Hg2+ in the pores of Pyridine-COF was mainly chelation not covalent interactions. Pyridine-COF represents one of the best COF-based adsorbents developed to date for the removal of Hg2+ from water.
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