Tea polyphenol and HfCl4 Co-doped polyacrylonitrile nanofiber for highly efficient transformation of levulinic acid to γ-valerolactone

Design catalytic materials with high Lewis acid/base sites for catalytic transfer hydrogenation (CTH) of levulinic acid (LvA) to γ-valerolactone (GVL) is highly demanded but challenging. Herein, we report a concept of metal ion-polymer hybridization to design a tea polyphenol (TP) and HfCl 4 co-doped polyacrylonitrile (PAN) nanofiber (Hf@PAN-TP) via electrospinning technique. Comprehensive characterization revealed the well coordination between hafnium ions and phenolic hydroxyl groups of TP on PAN fiber, which promoted the formation of Lewis acid and Lewis base sites. As expected, a satisfactory GVL yield of 99.1% with 100% of LvA conversion was obtained using isopropanol as a hydrogen donor at 170 °C in 5 h, and the catalytic activity remained unchanged for five cycles. The kinetic study revealed the lower activation energy for CTH of LvA to GVL (33.5 kJ/mol), demonstrating the outstanding GVL formation rate of 3383.9 μmol/g . h. Based on the systematical combine of catalyst characterization and catalytic behavior, the structure-function relationship and reaction mechanism were proposed. More gratifyingly, Hf@PAN-TP was applicable for catalytic reduction of various carbonyl compounds, demonstrating a great potential for upgrading biomass-derived aldehydes/ketones. The concept of metal ion-polymer hybridization to design Hf@PAN-TP nanofiber and its application in CTH of LvA to GVL.