Thermal behaviour, sulfonation and catalytic activity of phenylene-bridged periodic mesoporous organosilicas

Abstract

The structural and surface changes in a phenylene-bridged periodic mesoporous organosilica after thermal treatment under different conditions are reported. Organic moieties in the pore walls are stable at temperatures close to 500 °C but calcination in the presence of oxygen leads to C–Si bond cleavage as well as the formation of oxidized groups of phenolic and carbonyl type. The oxidized materials are functionalized by reaction with chlorosulfonic acid in a higher extension than those calcined under nitrogen but all of them preserve their structure and surface properties. All sulfonated organosilicas were active as catalysts for the esterification of acetic acid with ethanol, particularly those calcined in the air. Remarkably, some of them can be even more active than Amberlyst-15 when water is used as reaction medium which is of a high interest for the design of sustainable acid-catalyzed chemical processes.