Enhanced catalysis for degradation of rhodamine B by amino-functionalized Fe-MOFs with high adsorption capacity

Activation of peroxydisulfate (PDS) by iron-based metal organic frameworks (Fe-MOFs) presents a promising method to degrade various environmental contaminants. Herein, a series of environmentally friendly Fe-MOFs with different topological structures were synthesized and compared as catalysts for rhodamine B (RhB) removal process. The results indicated that amino-functionalized Fe-MOFs possessed large specific surface area and high affinity for RhB, which significantly improved the high adsorption capacity of RhB and PDS. It is found that NH2-MIL-101(Fe), containing Fe3-μ3-oxo clusters, showed high adsorption ability and excellent catalytic degradation of RhB. The efficient charge transfer from -NH2 to Fe-O clusters could efficiently accelerate Fe(II)/Fe(III) cycle. That is, NH2-MIL-101(Fe) was proved to be the most effective catalyst for removing RhB with a removal rate of 93%. The first-order kinetic constant (0.016 min−1) of NH2-MIL-101(Fe) was 2 times that of MIL-101(Fe). Singlet oxygen (1O2) was the main active species. Additionally, according to liquid chromatograph mass spectrometer (LC-MS) analysis, the degradation of RhB was mainly related to chromophore cleavage. This study guides for designing high-performance catalysts by introducing electron donating groups in organic dyes wastewater treatment.