Mesoporous surface-functionalized silicas and their application in sorption and catalysis

The chapter provides an overview of synthetic approaches and applications in sorption and catalysis of mesoporous surface-functionalized silicas. We have synthesized a series of the mono- and bifunctional SBA-15 samples with thiol, phosphonic and amino groups in their surface layer. All of them were obtained by direct template method using P123. To determine the concentration of chemically available functional groups on the surface of silica samples the method of potentiometric titration was used. The samples with phosphonic and thiol groups for lead (II) sorption were used and cumulative effect of them was described. The value of the distribution coefficient and the exchange constant for lead (II) ions for bifunctional samples were higher than for monofunctional analogues. This indicates that the bifunctional samples are more versatile sorbents. The maximum value of the static sorption capacity to Hg (II) ions was 390 mg/g, to Pb(II) ions ‒ 150 mg/g, to uranyl-ions – 201 mg/g, and to Nd(III) ions ‒ 78 mg/g. Catalytic tests of ethanol conversion have shown that the anchoring of phosphomolybdic acid on SBA-15 functionalized with aminopropyl groups enhances oxidizing properties of heteropolycatalysts. Accordingly, the supported catalysts are characterized by higher turnover frequency values in aerobic oxidation of cyclooctane to cyclooctanone and cyclooctanol.