Defect-Engineered UiO-66 Doped with Heterovalent Metals for Enhanced SO₂ Adsorption via Increased Active Sites

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• UiO-66 metal-organic frameworks (MOFs) show promise for gas adsorption but suffer from limited active site accessibility due to their microporous structure.
• Improving the chemical stability and active site accessibility of MOFs is crucial for practical applications like industrial flue gas purification.

Purpose of the Study:

• To engineer defect-rich UiO-66 frameworks using a postsynthetic heterovalent metal doping strategy.
• To enhance the SO2 adsorption capacity and chemical stability of UiO-66 for industrial applications.

Main Methods:

• Formic acid was used as a modulator to create defects in UiO-66.
• Postsynthetic heterovalent doping with Mn2+ was employed to create Mn-UiO-66-3.
• Systematic optimization and characterization of the material's structural robustness, thermal stability, and SO2 adsorption performance were conducted.

Main Results:

• Mn-doped Mn-UiO-66-3 demonstrated excellent structural robustness in acidic and basic media and thermal stability up to 400 °C.
• A 77% enhancement in SO2 adsorption capacity was achieved (1.111 mmol·g-1) compared to pristine UiO-66 (0.628 mmol·g-1).
• Cooperative interactions between defect sites and Mn2+ Lewis acid centers were identified as key to increased active site density and adsorption performance.

Conclusions:

• Heterovalent metal doping is an effective defect-engineering strategy for enhancing MOF host-guest interactions.
• Engineered defect sites and Lewis acid centers synergistically boost SO2 adsorption capacity.
• This work provides valuable insights into SO2 capture mechanisms and advances MOF design for flue gas purification.