Synergistic NiCo-BTC Catalysts for the Catalytic Transfer Hydrogenation of Furfural to γ-Valerolactone: Insights from Monometallic Cu-, Ni-, and Co-BTC Comparison

Abstract

A series of monometallic Cu-BTC, Ni-BTC, and Co-BTC catalysts was successfully synthesized via the solvothermal method to evaluate their performance in the catalytic transfer hydrogenation of furfural (FF) to γ-valerolactone (GVL). The Co-BTC and Ni-BTC catalysts exhibited higher FF conversion, selectivity, and GVL yield than Cu-BTC due to favorable redox properties of Co2+ and Ni2+ and stronger acidity that enhance substrate activation and key ring-opening and lactonization steps. To further enhance performance, bimetallic NiCo-BTC catalysts with different Ni/Co mole ratios (0.25, 0.50, 0.75, 1.00) were developed. All bimetallic NiCo-BTC catalysts outperformed the monometallic counterparts, with 0.50NiCo-BTC achieving complete FF conversion and the highest GVL selectivity and yield of 89% at 200 °C after 24 h. TEM, XPS, XANES, and NH3-TPD analyses indicated that the enhanced catalytic activity and selectivity arise from synergistic Ni-Co interactions and increased surface acidity. Time-resolved product analysis confirmed a sequential pathway with furfuryl alcohol (FA) as a key intermediate. Moreover, the 0.50NiCo-BTC catalyst exhibited good reusability over three cycles with minimal activity loss, demonstrating structural stability under reaction conditions. These results highlighted the importance of metal synergy and acid site tuning in designing highly efficient metal organic framework catalysts for biomass upgrading via catalytic transfer hydrogenation.