Pore engineering of MOF-808 for effective adsorption of roxarsone

The development of high-efficiency adsorbents for the removal of roxarsone from wastewater is necessary but remains difficult. Herein, a strategy of pore engineering was applied by using trifluoroacetic acid (TFA), formic acid (FA), and acetic acid (AA) as modulators to construct defective MOF-808. Physicochemical characterizations show that the type of acid modulators as well as their dosages has an impact on the material's structure defect. Benefiting from these defective units, the diffusion and mass transfer of roxarsone in the material can be promoted. Particularly, MOF-808-AA-b with the most defects exhibits the highest adsorption capacity (860.8 mg g−1) and rapid adsorption equilibrium (360 min). The adsorption isotherm and adsorption kinetics conform to Langmuir isotherm model and pseudo-second-order kinetic model, respectively. Adsorption thermodynamics indicates that the adsorption process was spontaneous and endothermic. Experimental characterization and density functional theory calculation jointly demonstrate electrostatic attraction, hydrogen bonding, π-π interactions, coordination interaction and pore-filling promote the roxarsone adsorption on MOF-808-AA-b. Additionally, this adsorbent possesses excellent chemical stability, outstanding anti-interference ability and regeneration-recycling performance. Thus, our work provides a powerful guidance in the optimization of modulators for constructing a high-efficiency adsorbent.