Preparation of Highly Active Triflic Acid Functionalized SBA‐15 Catalysts for the Synthesis of Coumarin under Solvent‐Free Conditions

Abstract

Highly acidic SBA‐15 with different pore diameters has been prepared by functionalizing the mesoporous walls with different amounts of triflic acid (TFA). The structure of the SBA‐15 before and after the functionalization with TFA was investigated by powder X‐ray diffraction and nitrogen adsorption isotherms. The interaction of TFA with the surface silanol groups of SBA‐15 and the acidity of the materials have been investigated by FTIR spectroscopy and temperature‐programmed desorption of ammonia, respectively. The characterization results reveal that the mesoporous structure of the SBA‐15 is retained even after the loading of TFA in the mesochannels and that the TFA molecules are bonded with the surface silanol groups of the SBA‐15 supports. The acidity of the materials increases with increasing amount of TFA from 5 to 20 wt %. These functionalized, highly acidic materials are found to be highly active in the synthesis of coumarin and the catalytic efficiency was found to correlate with the total acidity or the amount of TFA in the porous channels of the SBA‐15 catalysts. It has also been found that the activity of the TFA‐functionalized SBA‐15 in the synthesis of coumarin is much higher than that of different zeolites, pure mesoporous silica SBA‐15, and other mesoporous catalysts used in this study.

Conversion of Fructose and Xylose into Platform Chemicals Using Organo‐Functionalized Mesoporous Material

“…Kalita et al. carried out many organic reaction e. g. synthesis of coumarin, ring opening of epoxide by oxygen nucleophiles and addition of indoles to α, β‐unsaturated carbonyl compounds catalyzed by triflic acid (TFA) functionalized over different mesoporous materials . Besides, Kalita et al.…”

“…This trend finds the correlation with the increase in the density of acid site on the surface of the TFA functionalized KIT‐5 catalysts. We observed similar trend in our previous report using the same triflic acid functionalized over mesoporous materials for carrying out important organic reactions . The importance of TFA functionalization over KIT‐5 material could be seen when comparing the results obtained with the simple KIT‐5 catalyst (Table ) for this particular reaction.…”

Triflic Acid Functionalized Carbon@Silica Composite: Synthesis and Applications in Organic Synthesis; DFT Studies of Indeno[1,2‐b]indole

“…The FTIR spectrum of C Star @SiO 2 ‐TfOH exhibited a broad band at 3283 cm −1 that corresponds to phenolic –OH groups of the polyaromatic carbon rings and the band at 1711 cm −1 was assigned to C=O stretching of carboxylic acid groups.The band at 1452 cm −1 corresponds to the asymmetric stretching vibration of SO 2 group present in triflic acid, which was also absent in spectra of C Star @SiO 2 , there by confirming the grafting of triflic acid onto carbon@silica composite . Further, the band observed at 1512 cm −1 was due to aromatic C=C stretching modes.The band at 1602 cm −1 corresponds to the sharp bending mode of water molecules, which is absent in the spectra of C Star @SiO 2 ( b ).The characteristic absorption bands at 1102, 969 and 805 cm −1 were due to asymmetric vibrations of Si−O, asymmetric vibrations of Si‐OH and symmetric vibrations of Si−O . The band observed at 646 cm −1 corresponds to the C−S bond of the grafted triflic acid onto carbon@silica composite.…”

“…have developed triflic acid functionalized SBA‐15 catalysts by the functionalization of mesoporous walls of SBA‐15 with different amounts of triflic acid. The developed catalytic system has been used for the Pechmann reaction of resorcinol and ethylacetoacetate …”

SBA‐15 Supported Chiral Phosphine‐Gold(I) Complex: Highly Efficient and Recyclable Catalyst for Asymmetric Cycloaddition Reactions

“…All the samples prepared after each modification displayed typical type IV sorption isotherms with H1 hysteresis loops, suggesting that all samples are of mesoporous structure. [33] The amount of the adsorbed N 2 decreased gradually with each of the modification step. The textural properties and pore size distributions of these materials were shown in Table 1 and Figure 2 area, pore volume and average pore diameter decreased gradually after each successive immobilization process.…”