A Carboxyl-Functionalized Covalent Organic Framework Synthesized in a Deep Eutectic Solvent for Dye Adsorption

Area of Science:

• Materials Science
• Green Chemistry
• Environmental Science

Background:

• Traditional organic solvents pose environmental risks.
• Covalent organic frameworks (COFs) show promise for pollutant adsorption.
• Developing sustainable synthesis methods for functional materials is crucial.

Purpose of the Study:

• To synthesize a carboxyl-functionalized COF using a deep eutectic solvent (DES).
• To evaluate the COF's performance in selectively adsorbing organic dyes from wastewater.
• To explore the underlying adsorption mechanisms and capacities.

Main Methods:

• Synthesis of a carboxyl-functionalized COF (TpPa-COOH) using a tetrabutylammonium bromide and imidazole (Bu4NBr/Im) DES.
• Characterization of the synthesized COF.
• Adsorption experiments using eosin B (anionic), methylene blue (cationic), and safranine T (cationic) dyes.
• Analysis of adsorption isotherms using the Langmuir model.

Main Results:

• A novel carboxyl-functionalized COF (TpPa-COOH) was successfully synthesized under ambient pressure using a DES.
• TpPa-COOH exhibited selective adsorption of cationic dyes (methylene blue and safranine T) over an anionic dye.
• The COF demonstrated high adsorption capacities for safranine T (1135 mg/g) and methylene blue (410 mg/g), attributed to electrostatic, π-π interactions, and hydrogen bonding.

Conclusions:

• Deep eutectic solvents offer a green alternative for synthesizing functional COFs.
• The synthesized TpPa-COOH is an effective adsorbent for selectively removing cationic dyes from wastewater.
• This study provides a sustainable approach for developing adsorbents for environmental applications.