Cooperative activation of H2 with H2O or NH3 enables efficient furfural upgradation over Ni2P/REPO4 catalysts: a family feature of lanthanide rare-earth phosphates†

The innovation of effective catalysts capable of cooperatively activating multiple small molecules is of great importance for boosting the corresponding chemical upgradation. Here, the potential of lanthanide rare-earth phosphates (REPO₄) for activating H₂, H₂O and NH₃ was demonstrated by integrating nine rare-earth components (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, and Y) in Ni–RE–P catalysts for converting furfural into cyclopentanone (CPO) or furfurylamine (FFA). ICP-OES, XRD, XPS, SEM, and HRTEM characterizations revealed that these catalysts possessed a structure of Ni₂P supported on REPO₄ (Ni₂P/REPO₄), with an Ni mass loading of around 10%. Under mild pressures of 0.5–1.0 MPa, significant enhancements in catalytic performance were exhibited by the Ni₂P/REPO₄ catalysts versus Ni₂P/SiO₂, such as 75–90% vs. 4% in terms of CPO yield and 67–99% vs. 22% in terms of FFA yield. These results position Ni₂P/REPO₄ among the top-performing catalysts reported to date. Using isotope tracing, in situ IR spectroscopy, TPD-MS measurements and DFT calculations, the catalytic superiority of Ni₂P/REPO₄ could be attributed to its ability to cooperatively activate H₂ with H₂O or NH₃ using REPO₄. Specifically, RE and O sites on REPO₄ could function as acid–base pair sites with comparable distribution and strength, essential for facilitating the cooperative activation of these small molecules and facilitating the complicated mechanism for the three-molecule-involved furfural upgradation conversions. These results highlighted the family feature of REPO₄ as a versatile and efficient component for catalytic transformations involving multiple small molecules, providing a new reference for designing outstanding multi-functional catalytic systems with a simple composition to advance the corresponding chemical engineering applications.