Insights into the Enhanced Tetracycline Adsorption by Two-Dimensional Cu-Based Metal-Organic Framework

Area of Science:

• Environmental Chemistry
• Materials Science
• Nanotechnology

Background:

• Tetracycline (TC) contamination in aquatic environments presents a significant ecological and human health risk.
• Efficient technologies for TC removal are urgently needed.
• Two-dimensional metal-organic frameworks (2D MOFs) offer tunable structures and active sites for adsorption applications.

Purpose of the Study:

• To synthesize and evaluate three isostructural 2D MOFs, M3(HHTP)2 (M = Cu, Ni, Co), for tetracycline adsorption.
• To elucidate the adsorption mechanism and identify factors influencing adsorption performance.
• To provide insights for designing high-performance 2D MOFs for pollutant removal.

Main Methods:

• Solvothermal synthesis of three isostructural 2D MOFs: Cu3(HHTP)2, Ni3(HHTP)2, and Co3(HHTP)2.
• Adsorption experiments to determine TC adsorption capacity and kinetics.
• Langmuir isotherm and pseudo-second-order kinetic modeling to analyze adsorption behavior.
• Mechanistic investigations, including analysis of metal center electronic structure and surface functional groups.

Main Results:

• Cu3(HHTP)2 demonstrated a superior TC adsorption capacity of 302.84 mg/g.
• Adsorption followed Langmuir isotherm and pseudo-second-order kinetics, indicating chemisorption.
• Jahn-Teller distortion in Cu2+ sites created high-activity coordination sites, crucial for TC adsorption.
• Synergistic effects from surface functional groups and pore structure enhanced adsorption.
• Metal center electronic structure was identified as the key factor determining differential adsorption performance.

Conclusions:

• Cu3(HHTP)2 is a highly effective adsorbent for tetracycline removal from water.
• The adsorption mechanism involves strong coordination with Cu2+ sites, hydrogen bonding, and favorable pore structure.
• The electronic structure of the metal center significantly influences the adsorption behavior of 2D MOFs.
• This study offers valuable guidance for designing advanced 2D MOFs for environmental remediation.