Ethoxylated FSM-type mesoporous silica (folded-sheet mesoporous material) with a pore diameter of 6.2 nm (FSM6.2) remarkably enhances rigidly of the structure in aqueous solutions. The esterified material could be used successfully as an adsorbent to accommodate subunit protein, methemoglobin (Fe3+). Furthermore, methemoglobin (Fe3+) in the pores of ethoxy-FSM is maintained a peroxidase activity similar to the native, indicating methemoglobin retains its fore subunit structure in the pores of FSM6.2.