Enhancing methyl orange adsorption capacity via functionalizing ZIF-8 with amphiphilic cetylpyridinium bromide

Background The precise design or functionalization of metal organic frameworks (MOFs) based on the properties of organic dyes is a promising direction in environment remediation. Methods Herein, using methyl orange (MO) as the target dye, cetylpyridinium bromide (CPB) functionalized ZIF-8 (CPB@ZIF-8) was fabricated by the post-synthetic modification strategy. Significant findings The surface area and the pore volume of CPB@ZIF-8 are greatly reduced compared with pure ZIF-8. However, the introduction of amphiphilic CPB molecules into ZIF-8 can significantly enhance the adsorption performance of MO. This enhanced MO adsorption capacity can be attributed to the incorporation of more positively charged sites, hydrophobic sites and aromatic rings in the CPB-modified ZIF-8 frameworks, which provides the electrostatic attractions, the hydrophobic and π-π interactions that mainly govern the adsorption of MO on CPB@ZIF-8. The pseudo-second-order kinetic model and the Langmuir isotherm model can well represent the adsorption process of MO. The maximum adsorption capacity (195.54 mg/g) has been obtained at 30 °C, outperforming pristine ZIF-8 and various reported absorbents. The prepared CPB@ZIF-8 composite is a superior example of the tunable adsorption affinity of MOFs for anionic dyes.