Ordered multi-modal sulfated MOF-808 and its improved catalytic performance in glycerol esterification

Abstract

Ordered and interconnected multimodal metal–organic frameworks (MOFs) offer a compelling platform for catalytic applications, particularly in liquid-phase esterification. In this work, we investigate the structure–function relationship in MOF-808 modified through surfactant-assisted porosity engineering and post-synthetic sulfation, to target the esterification of glycerol with acetic acid. The use of a surfactant during synthesis promoted hierarchical porosity by combining micropores and macropores without diminishing the native acidity of the material. Subsequent sulfation introduced additional and stronger Brønsted acid sites while essentially preserving the ordered porous architecture. Catalytic performance under iso-conversion conditions at approximately 65% glycerol conversion revealed that efficient triacetin formation occurs only when both non-micropore uniformity and acid strength are simultaneously optimized. Comprehensive characterization using X-ray diffraction, nitrogen physisorption, infrared spectroscopy, and acid site quantification evidenced the presence of tailored acid functionalities and the preservation of structural features of the framework. Overall, this study identifies the combined roles of multimodal porosity and acid site engineering in determining catalytic selectivity, providing design principles for developing MOF-based acid catalysts with enhanced accessibility and molecular control.