One-pot acid–base catalysed tandem reactions using a bimodal N, S-doped cubic mesoporous carbon

Abstract

Inspired by the synergistic collaboration of multiple active sites in living systems, a novel bifunctional acid–base ordered mesoporous carbon denoted as “Ionic liquid derived Bimodal cubic Ordered Mesoporous Carbon” (IBOMC) was designed using a nanocasting protocol with KIT-6 as a hard template and a mixture of 1-methyl-3-phenethyl-1H-imidazolium hydrogen sulfate (MPIHS) and guanine as ionic liquid and nitrogen-rich organic precursors, respectively. High basicity and acidity, a high surface area, good thermal resistance, a well-defined pore size, and high nitrogen content constitute the most remarkable features of this carbon and have never been observed altogether in other reported carbons. The dual acid–base characteristic of the designed porous carbonaceous material was verified in the selective one-pot tandem deacetalization–Knoevenagel condensation of acetals with malononitrile, a feature that was attributed to its unique 3D bimodal structure as well as the presence of both strong acidic and basic functional groups in its framework. This material was also employed as a robust acid catalyst in the synthesis of 5-HMF (5-hydroxymethylfurfural) from fructose with 98% yield. IBOMC exhibits excellent bi-functional activity in the conversion of glucose into 5-HMF with 45% yield; this has also been extended to 5-HMF production from sucrose and cellulose. This study highlights the importance of topology and the balance between the strength of acid and base functional groups of catalysts in tandem reactions.