Mesoporous silica materials are attractive candidates for enzymes immobilization due to their high surface area, tunable pore size, large pore volume and biocompatibility. In this work, two different enzymes, papain, a small globular enzyme with molecular diameter of 3.6nm, and catalase, a relatively larger enzyme with molecular diameter of 10.4nm were introduced into the pores of siliceous mesostructed cellular foams (MCFs) that had a large cellular pores of 29nm and a small window size of 12nm, respectively. The amount of adsorbed enzymes was found to be dependent on the molecular size of enzymes. The amount of adsorbed catalase was more than two times that of adsorbed papain, suggesting that MCFs with large pores is a suitable host for large enzymes adsorption. The blocking of pores which resulted from aggregation of enzymes in the windows of MCFs and the higher leaching of enzymes form MCFs may be the reason of lower papain adsorption capacity in MCFs.