Accurate restricted transition-state shape selective hydrogenation of furfural over zeolite confined Cu catalyst

Transition-state shape selectivity plays a crucial role in catalytic systems where reactants and products exhibit comparable molecular dimensions, as it restricts the accessible configuration space of reaction intermediates. Efficient conversion of the biomass-derived platform molecule furfural is significant, but its hydrogenation to furfuryl alcohol often suffers from undesired Piancatelli rearrangement, forming cyclopentanone and cyclopentanol. Recently, a research team led by Prof. Yao Fu from the University of Science and Technology of China developed a Cu@MFI catalyst via a pore-confinement strategy. Copper species were encapsulated within the intersecting 10-membered ring (10 MR) channels of MFI zeolite via a rapid high-temperature hydrothermal synthesis method, constructing a Cu@MFI catalyst that integrates framework integrity, unobstructed mass transport channels, and bifunctional active sites. Structural characterization confirmed the coexistence of copper as single atoms (Cu within cages) and binuclear oxo-bridged species ([Cu₂(μ-O)_x]²⁺ clusters within the 10 MR channels), without pore blockage or framework damage.

Compared to catalysts prepared by conventional impregnation (Cu/S-1, Cu/SiO₂) and large-pore zeolite Cu@MOR, Cu@MFI exhibited exceptional catalytic performance in the aqueous-phase hydrogenation of furfural: it achieved 100% furfural conversion and 100% furfuryl alcohol selectivity at 70 °C, with activity maintained stably over a broad temperature range of 50–150 °C. In contrast, the other catalysts generated side products (cyclopentanone and cyclopentanol). Combined DFT calculations and experimental validation revealed the structure-performance relationship and reaction mechanism: (1) Synergistic Bifunctional Active Sites: Cage-confined Cu single atoms preferentially dissociate H₂, while channel-located binuclear Cu clusters synergistically polarize the C=O bond via d-π conjugation and σ-bonding, lowering the hydrogenation energy barrier (0.31 eV for furfural to furfuryl alcohol vs. 0.45 eV on Cu(111)). (2) Transition-State Confinement Effect: The MFI 10 MR channels impose steric constraints on bimolecular transition states (the Piancatelli rearrangement intermediate involving furfuryl alcohol and H₂O), significantly raising its energy barrier (2.13 eV vs. 0.17 eV on open Cu surfaces), thereby blocking the side reaction pathway.

Furthermore, introducing trace Pt (0.2 wt%) accelerated hydrogen spillover, reducing the reaction time to 2 hours while maintaining 100% conversion and selectivity without compromising the confinement functionality. This work presents an efficient catalytic system for biomass valorization via precisely confined bifunctional sites and transition-state configuration control. The strategy is potentially applicable to other reactions involving bulky transition states and offers a new paradigm for resolving the ubiquitous activity-selectivity-stability trade-off in heterogeneous catalysis. The results were published in Chinese Journal of Catalysis (DOI: 10.1016/S1872-2067(25)64741-3).

About the Journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top one journals in Applied Chemistry with a current SCI impact factor of 17.7. The Editors-in-Chief are Profs. Can Li and Tao Zhang.

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