Catalytic conversion of glucose to furfural via asymmetrical C-C bond scission: Insight into the location and configuration of framework Sn species

Tandem isomerization and decarbonylation increased furfural yield from 34.4% to 67.9%. • Framework Sn location was governed by T-vacancy distribution in dealuminated H-beta. • Open Sn sites at pore mouths improved furfural selectivity. The asymmetric C-C bond scission of C6 glucose to C5 furfural via a “C5 + C1” retro-aldol pathway represents a promising and important route for the valorization of bio-based sugar resources. However, this transformation still faces major challenges in achieving high selectivity and efficiency, as stable glucopyranose tends to undergo side reactions leading to oligomeric humins. In this work, to enhance furfural yield, Sn atoms were incorporated into the framework of dealuminated H-beta zeolite to construct synergistic active sites for coupling isomerization and decarbonization reactions. The catalytic performance was found to be highly sensitive to the type, spatial location, and coordination environment of framework Sn species. Based on Low-Energy Ion Scattering (LEIS) and X-ray absorption fine structure (XAFS) results, it is demonstrated that open Sn sites located at the pore mouths of H-beta zeolite are conducive to the conversion of glucose into furfural via coupled isomerization-decarbonization pathways. Accordingly, Sn-Al-beta-C, which possesses the highest proportion of open Sn sites, achieves the highest furfural yield of 67.9% at nearly complete glucose conversion, markedly outperforming H-beta (34.4%) and the corresponding physical mixtures. The ratio of open to closed Sn sites can be regulated by controlling the deposition of Sn (IV) species at the pore mouths of H-beta zeolite. The results of this work demonstrate the feasibility of constructing metal–acid bifunctional sites for the direct conversion of glucose to furfural and provide valuable insights for the rational design of efficient metal-modified zeolite catalysts.