A 2-Fold Interpenetrated Nitrogen-Rich Metal-Organic Framework for Rapid and Selective Adsorption of Congo Red

A new metal-organic framework was prepared based on a mixed ligand system of the designed nitrogen-rich 3,6-bis(2-methylimidazole)pyrimidine (b2mpm) and benzophenone 4,4'-dicarboxylic acid (H₂bpndc). The prepared material shows a three-dimensional 2-fold interpenetrated pcu framework and features rectangular channels decorated with nitrogen sites. Thanks to the abundant hydrogen bonding and π-π stacking interactions, the titled material can rapidly adsorb Congo red (CR) and presents ultrahigh adsorption capacity (2348 mg g^-1). Moreover, this material has an adsorptive selectivity toward CR and can be regenerated by simply washing it with ethanol. The adsorption kinetic and isotherm of the titled material were also determined, indicating that the adsorption kinetic conforms to the pseudo-second-order model and the adsorption isotherm obeys the Langmuir model. Additionally, the titled material exhibits the suitable adsorption ability toward CO₂ (15.2 cm³ g^-1 under 1 atm at 298 K). These results demonstrate that the titled material would be an effective and easily regenerated adsorbent for CR removal from wastewater.