Acid-engineered UiO-66(Ce): From the limitations of concealed MOF sites to catalytic excellence for rapid atrazine degradation

Metal-organic frameworks (MOFs) hold promise for catalytic ozonation in environmental remediation; however, their application is hindered by limited active site exposure and structural instability. This study introduces a novel acid-assisted ligand engineering approach to enhance the accessibility of the metal sites in UiO-66(Ce), a Ce–MOF catalyst. By substituting formic acid with certain organic ligands (terephthalic acid) and subsequent hydrochloric acid treatment, we synthesized UiO-66-F-H, a modified catalyst that exhibited significantly increased Lewis acid sites and enhanced structural robustness. Comparative analyses demonstrated that UiO-66-F-H achieved an atrazine degradation rate 5.7 times higher than that of its unmodified counterpart and 17.7 times that of ozonation alone under the optimal experimental conditions (pH = 7.0, T = 10 ℃, and [O₃] = 3 mg L⁻¹). The characterization results confirmed a 40% increase in the number of surface Lewis acid sites and a notable improvement in catalyst stability, which was attributed to the exposed coordinated unsaturated Ce metal sites. The enhanced catalytic performance, coupled with superior stability and recyclability, suggests that UiO-66-F-H is a promising candidate for broader environmental applications, introducing a new paradigm for MOF modification. This study addresses the critical limitations of MOFs in catalytic ozonation and fosters the development of sophisticated MOF-based materials tailored for environmental remediation applications.