A new type bimetallic NiMn-MOF-74 as an efficient low-temperatures catalyst for selective catalytic reduction of NO by CO

Focus on providing a low temperature noble metal free CO-SCR catalyst, a series of Ni-Mn mixed bimetal–organic frameworks catalysts were synthesized using solvothermal method. Compared to monometallic Ni or Mn-MOF-74, a significant improvement of catalytic performance was found over bimetallic NiMn-MOF-74. Especially, Ni0.65Mn0.35-MOF-74 catalyst achieved a nearly 100 % NO conversion at 175 °C with a nearly 100 % N2 selectivity at 200 °C. By combining XRD, Raman, XPS and H2-TPR results, it was found that the synergistic effect between Ni and Mn species was beneficial for the formation of more active Mn4+ and Ni3+ components and Lewis acid sites for NO elimination. In addition, the enhanced low-temperature SCR activity can be attributed to the high BET surface, expansion of crystal lattice, increase in adsorbed NO/CO species and more surface oxygen vacancies. Based on in situ FT-IR analyses, the generation of N2O which are identified as an important byproduct and a possible L-H mechanism for NO reduction by CO over NiMn-MOF-74 was proposed.