Recyclable Textile Fiber-Supported N-Heterocyclic Carbene Catalyst for Upgrading of Biomass Furaldehydes to Jet-Fuel Precursors

The exploitation of cleaner catalytic technologies with high efficiency for the upgrading of biomass-derived furaldehydes is one of the crucial routes to the high-value utilization of biomass resources. Herein, the textile fiber polyetheretherketone (PEEK) was employed as a support for the immobilization of thiamine chloride (VB1), and the resulting PEEK-supported VB1 (PEEK-VB1) is capable of acting as a recyclable N-heterocyclic carbene (NHC) catalyst for the selective umpolung acyloin condensation of furfural and 5-hydroxymethylfurfural (HMF) into C 10 and C 12 furoins, which serve as jet-fuel precursors. The functionalized fiber materials were comprehensively characterized through morphological analysis, mechanical property testing, X-ray diffraction, elemental analysis, Fourier transform infrared (FTIR) spectroscopy, photoelectron spectroscopy, and thermogravimetric analysis. Moreover, the afforded fiber catalyst with hydrophobicity was very beneficial for enriching the organic substrates into its backbone, which would promote the reaction in the surface layer of the fiber. Furthermore, PEEK-VB1 as the precatalyst could be activated in situ by base to generate a fiber-supported NHC catalyst, which was stable in an alkali solution and further to accelerate the conversion of furaldehydes into furoins with yields over 98% in an aqueous system, and could be recycled by quenching the reaction with HCl to convert the NHC back to PEEK-VB1 with good recyclability. What is more, the unique architectures and robust mechanical properties of PEEK-VB1 enabled its scalability to gram-level production, offering a cleaner approach for transforming biomass furaldehydes into jet-fuel precursors with good prospects for industrial application.