Single-step preparation of zinco- and aluminosilicate delaminated MWW layers for the catalytic conversion of glucose

Abstract

Two-dimensional (2D) molecular sieves with highly dispersed active centers have great potential as catalysts for the transformation of bulky biomass derivatives owing to the ease of molecular diffusion and the deactivation resistance by coke deposition. Here, we report a single-step preparation of a 2D Lewis acidic zincosilicate delaminated MWW layer (Zn-DML) and Lewis-Bronsted acidic ZnAl-DML catalysts by a simple hydrothermal treatment of a borosilicate MWW precursor with Zn and/or Al precursor solutions. Both framework Zn and ultra-small Zn clusters are highly dispersed in Zn-DML, while framework Al species prevail over Zn in ZnAl-DML catalysts. Zn-DML catalysts are more delaminated than ZnAl-DML catalysts. Density functional theory calculations show that heteroatom-substituted 2D MWW layers are more stable than their 3D analogues, and Al-containing systems are more stable than Zn. Lewis acidic Zn-DML was selective for fructose, whereas Lewis-Bronsted acidic ZnAl-DML catalysts were selective for 5-hydroxymethylfurfural in the catalytic glucose conversion.