Controlled synthesis of MOF-derived Ce–Ln mixed oxides: influence of lanthanide doping and supported Ni on CO₂ conversion through the reverse water gas shift reaction

The reverse water-gas shift (RWGS) reaction (CO 2 + H 2 ⇆ CO + H 2 O) is a key process for CO 2 valorization, providing a sustainable route to generate CO as an intermediate for methanol and Fischer-Tropsch syntheses. In this work, mixed ceria–lanthanide oxides derived from Ce–Ln RPF-4 metal–organic frameworks (Ln = La, Nd, Pr) were prepared and evaluated as RWGS catalysts. The parent MOFs were synthesized solvothermally and calcined in air to yield solid solutions Ce 1-x Ln x O 2-x/2 with controlled compositions and high structural homogeneity. The influence of the dopant nature (Ln) and proportion was systematically studied, as well as the effect of incorporating Ni(10 mol%) by impregnation. Characterization by PXRD, Raman spectroscopy, TPR, XPS, and TEM confirmed that La 3+ , Pr 3+ , and Nd 3+ ions substitute Ce 4+ in the fluorite lattice, generating oxygen vacancies that enhance reducibility and oxygen mobility. The Ce La 8:2 composition showed the most favorable balance between defect density and lattice stability, achieving the highest CO₂ conversion and CO selectivity. Ni addition markedly increased activity due to the bifunctional synergy between metallic Ni sites for H₂ activation and the doped ceria support for CO₂ adsorption and reduction. The best catalyst, Ni(10 mol%)/Ce–La 8:2, reached a CO formation rate of 2.2 mol h −1 g cat −1 with 98% CO selectivity at 700 °C under high space velocity (300 L/h gcat −1 ), 90 h, time-on-stream. These results demonstrate that MOF-derived Ce–Ln oxides constitute a versatile platform for designing efficient and compositionally tunable catalysts for CO₂ conversion via the RWGS reaction. • Ce-Ln (La, Nd, Pr) mixed oxides were synthesized via MOF-derived routes. • Ni 10 /Ce 80 Ln 20 catalysts show high activity and selectivity in the RWGS reaction. • Rare earth doping enhances oxygen mobility and CO 2 activation. • Ni nanoparticles promote H 2 dissociation and synergize with Ce-Ln supports. • Catalysts exhibit good thermal stability at 700 °C.