Periodic mesoporous organosilicas with 1,4-diethylenebenzene in the mesoporous wall: Synthesis, characterization, and bioadsorption properties

The 1,4-diethylenebenzene-bridged mesoporous organosilicas and bifunctional periodic mesoporous organosilicas with various amounts of 1,4-diethylenebenzene and ethane bridging groups in the mesoporous wall were synthesized by a direct cocondensation method using P123 as structure-directing agent under acidic conditions. All the materials have ordered mesostructure with uniform pore size distributions. The BET surface area and pore diameter decrease as the amounts of 1,4-diethylenebenzene in the mesoporous wall increase. The composition of the mesoporous organosilicas was characterized by FT-IR, C-13 cross-polarization magic-angle spinning (CP-MAS) NMR, and Si-29 magic-angle spinning (MAS) NMR spectroscopy. The adsorption of lysozyme (Lz) on the resultant materials was studied at different pH values. All the adsorption isotherms have successfully been correlated by the Langmuir equation. The adsorption capacity of all materials reaches the maximum around the isoelectric point of Lz. It was found that the material with mixed composition of 1,4-diethylenebenzene and ethane in the wall exhibits higher adsorption amounts than the mesoporous ethane-silica, and the difference in the adsorption amounts between the two materials decreases as the solution pH increases, suggesting that the hydrophobic and hydrogen-bonding interaction between 1,4-diethylenebenzene and Lz is stronger than that between ethane and Lz, especially at lower pH value. FT-IR spectra of the adsorbed Lz confirm that the adsorption of Lz did not lead to the denaturation of enzyme in the pH range investigated.