Aminosilane-grafted SiO2-ZrO2 Polymer Hollow Fibers as Bifunctional Microfluidic Reactor for Tandem Reaction of Glucose and Fructose to 5-Hydroxymethylfurfural

In this study, we demonstrate the concept of tandem reaction for glucose and fructose to 5-hydroxymethylfurfural (HMF) in an aminosilane-grafted SiO2–ZrO2 polyamide–imide hollow fiber that acts as a bifunctional heterogeneous catalyst and microfluidic reactor. The bifunctional catalysts were formed by embedding SiO2 and ZrO2 nanoparticles into polyamide–imide polymer dope that underwent subsequent phase inversion through “dry-jet, wet-quench spinning” process to form hollow fibers, followed by postgrafting with aminosilane to incorporate amine moieties into the hollow fibers. The tandem strategy integrated the first step of glucose isomerization with the subsequent step of dehydration of fructose to HMF over bifunctional Lewis and Bronsted acid sites of hollow fiber microfluidic reactor at different temperatures (100–150 °C) and reaction times (1–8 h). Our results indicated, through optimizing the Lewis to Bronsted acid sites  ratio in hollow fiber catalysts, the HMF selectivity was enhanced from 21% to 8...