Metal-organic framework materials in NH3-SCR: Progress and prospects

Metal-organic framework (MOF) materials have emerged as promising catalysts in the selective catalytic reduction (SCR) of nitrogen oxides (NOx) using NH3. This review highlights the various types of MOF materials commonly applied in NH3-SCR processes, including UiO-66, MIL-101, MIL-100, HKUST-1 (Cu-BTC), ZIF-8, ZIF67, and other BTC series catalysts. Additionally, it provides a comprehensive analysis of the NH3-SCR denitrification (de-NOx) reaction mechanism occurring on MOF materials, encompassing active sites, intermediate states, and reaction processes. Furthermore, the review conducts a thorough analysis of the poisoning mechanisms of water, sulfur, alkali metal, and alkaline-earth metal that may occur during NH3-SCR reactions with MOF materials, along with strategies to enhance their tolerance to poisoning. The challenges that MOF materials face in NH3-SCR de-NOx applications are outlined, alongside prospective future directions and applications. Effective strategies, such as constructing protective sites, modifying coordination structures, tuning pore architectures, and designing multi-metal active centers, are proposed to improve the redox and acid cycles and the tolerance to poisoning in NH3-SCR reactions. In conclusion, MOF materials hold tremendous potential in de-NOx catalysis, but practical gaps relative to industrial demands remain. This review aims to bridge these gaps and enhance the feasibility and efficiency of their industrial applications. Attention is drawn to the importance of continued research and development to optimize these materials for practical use, ensuring they meet the robustness, durability, and performance required for large-scale implementation in NH3-SCR de-NOx technologies.