Facile design of highly effective Fe-modified bimetallic Fex–Ni1−x-MOFs catalysts with rodlike structures for low-temperature NO reduction by CO

A series of Fe-modified bimetallic Fex–Ni1−x-MOFs catalysts were successfully synthesized by solvent thermal method for CO-SCR. A significant activity improvement was found over bimetallic MOFs with the highest NOx conversion of 100% achieved on Fe0.33–Ni0.67-MOFs at 230 °C. The promoted low-temperature SCR activity was attributed to large surface area, directional growth of rod structure and greater surface oxygen mobility. The enhanced adsorption and transformation ability of CO and NO were further found due to relatively high concentration of Fe3+/Fe2+ formed due to redox cycle (Fe2+  + Ni3+ ↔ Fe3+  + Ni2+). Fe sites were found to be strong storing sites for NOx species helping to anchor more nitrates. A special Fe–Ov–Ni structure was formed between Fe and Ni, which can weaken N–O bond and generate more bridging nitrate, especially key intermediates trans-N2O2− species at low temperature. These features played a crucial role at low temperature and therefore achieved a superior activity.