Theoretical Exploration of the Competitive Mechanism for Hydrodehydration and Decarboxylation of 2,5-Furandicarboxylic Acid by Pt₁ and Pt₃ Supported on Nb₂O₅

How the size of the Pt-cluster over Nb2O5 affects the catalytic performance for the hydrodehydration of 2,5-furandicarboxylic acid (FDCA) is not yet clear at the molecular level. We rationally designed the Pt1/Nb2O5 ([Pt1]) and Pt3/Nb2O5 ([Pt3]) catalyst models. Over them, the catalytic mechanism for the hydrodehydration of FDCA to adipic acid (AA) has been theoretically investigated in aqueous solution at the GGA-PBE/DNP level together with its side reactions. The hydrodehydration of FDCA to AA is associated with the ring-opening of furan as the rate-determining step, whereas the decarboxylation of FDCA to furan is related to the cleavage of the C–C bond as the rate-determining step. For the conversion of FDCA, [Pt3] shows higher catalytic activity than [Pt1], because of the less positive charge of Pt1–Pt2 dual-sites over [Pt3] than that of the Pt1 single-site over [Pt1]. Here, the Pt1–Pt2 dual-sites over [Pt3] have a more important synergistic effect on the cleavage of both C5–O3 and C5–C6 bonds compared with the Pt single-site over [Pt1]. Furthermore, [Pt3] selectively favors the FDCA-to-AA hydrodehydration, whereas [Pt1] selectively promotes the FDCA-to-furan decarboxylation. The current research results should provide some theoretical clues for designing novel supported cluster metal oxide catalysts for the hydrogenation of biomass.