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Beyond Density: Unveiling the Trade-Off in Catalytic Site Optimization Using Defect-Engineered UiO-66
Guo-Ying Han1, Yi Ji2, Xiang-Yu Li3
1School of Chemistry, Dalian University of Technology, Dalian, 116024, China.
Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
|September 2, 2025
Summary
Increasing catalytic sites in metal-organic frameworks (MOFs) doesn't always boost performance. Too many sites can cause self-adsorption, hindering reactions and lowering catalytic activity.
Area of Science:
- Materials Science
- Catalysis
- Chemical Engineering
Background:
- Enhancing catalytic performance is crucial for chemical processes.
- Strategies include boosting intrinsic activity and increasing catalytic site density.
- The interplay between these strategies, particularly in metal-organic frameworks (MOFs), is not well understood.
Purpose of the Study:
- To investigate the relationship between catalytic site density and catalytic performance in UiO-66 MOFs.
- To compare linker-defective (UiO-66L) and cluster-defective (UiO-66C) UiO-66 MOFs with varying site densities.
- To elucidate the underlying mechanisms affecting catalytic activity and diffusion.
Main Methods:
- Synthesis of UiO-66L and UiO-66C MOFs with distinct catalytic site densities.
- Systematic comparison of catalytic activity across four model reactions.
- Diffusion-ordered spectroscopy (DOSY) and molecular dynamics (MD) simulations to study diffusion rates.
- Analysis of reactant self-adsorption effects.
Main Results:
- UiO-66L, despite higher Zr catalytic site density, showed lower activity than UiO-66C and defect-free UiO-66.
- UiO-66C exhibited similar diffusion rates to defect-free UiO-66.
- UiO-66L displayed significantly slower diffusion rates.
- High catalytic site density in UiO-66L led to reactant self-adsorption and local diffusion resistance.
Conclusions:
- A performance trade-off exists between catalytic site density and intrinsic activity in MOFs.
- Exceeding a critical threshold of catalytic site density can negatively impact catalysis.
- Defect engineering in MOFs requires careful consideration of site density effects on diffusion and overall performance.
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