Phosphotungstic acid (H3PW12O40 6H(2)O) was immobilized within a hierarchically structured silica matrix by sol-gel inclusion using polyethylene oxide as a phase separation initiator (one-pot synthesis). The macropore size of the SiO2-HPW composites was controlled by the polymer content. The hierarchically structured catalysts with different HPW loadings were tested against their counterparts with monomodal pore size distribution, applying the dehydration of glycerol as a test reaction. The catalysts with bimodal pore size distribution showed a significantly better long-term stability. The improved performance was attributed to their balanced acidity, excellent leaching stability, and enhanced mass transfer within the hierarchically structured pore system.