Conversion of CO into CO2 by high active and stable PdNi nanoparticles supported on a metal-organic framework

The solubility of Pd(NO 3 ) 2 in water is moderate whereas it is completely soluble in diluted HNO 3 solution. Pd/MIL-101(Cr) and Pd/MIL-101-NH 2 (Cr) were synthesized by aqueous solution of Pd(NO 3 ) 2 and Pd(NO 3 ) 2 solution in dilute HNO 3 and used for CO oxidation reaction. The catalysts synthesized with Pd(NO 3 ) 2 solution in dilute HNO 3 showed lower activity. The aqueous solution of Pd(NO 3 ) 2 was used for synthesis of mono-metal Ni, Pd and bimetallic PdNi nanoparticles with various molar ratios supported on MOF. Pd 70 Ni 30 /MIL-101(Cr) catalyst showed higher activity than monometallic counterparts and Pd + Ni physical mixture due to the strong synergistic effect of PdNi nanoparticles, high distribution of PdNi nanoparticles, and lower dissociation and desorption barriers. Comparison of the catalysts synthesized by MIL-101(Cr) and MIL-101-NH 2 (Cr) as the supports of metals showed that Pd/MIL-101-NH 2 (Cr) outperforms Pd/MIL-101-(Cr) because of the higher electron density of Pd resulting from the electron donor ability of the NH 2 functional group. However, the same activities were observed for Pd 70 Ni 30 /MIL-101(Cr) and Pd 70 Ni 30 /MIL-101-NH 2 (Cr), which is due to a less uniform distribution of Pd nanoparticles in Pd 70 Ni 30 /MIL-101-NH 2 (Cr) originated from amorphization of MIL-101-NH 2 (Cr) structure during the reduction process. In contrast, Pd 70 Ni 30 /MIL-101(Cr) revealed the stable structure and activity during reduction and CO oxidation for a long time.