Fe(III) complex anchored SBA-15 is a new heterogeneous catalyst for the cleavage of aliphatic CC bond of styrene and its derivatives

Heterogenization of homogeneous Fe-complex on a mesoporous silica SBA-15 has been designed to gain the benefits of both homogeneous and heterogeneous catalytic processes emphasizing the influence of two different coordinating ligands in catalytic applications. With this aim, Fe(III) Schiff-base complex containing both (i) acetylacetonate and (ii) H2salen ligands has been covalently anchored onto a mesoporous SBA-15 for the first time in three successive steps, (i) surface functionalization of SBA-15 with (3-aminopropyl)triethoxysilane, (ii) anchoring of Fe(III) acetylacetonate through Schiff-base condensation between the propylamine groups that functionalized with SBA-15 and carbonyl carbons of Fe(III) acetylacetonate, followed by (iii) tethering of H2salen ligand to F(III) acetylacetonate, leading to desired heterogeneous catalyst, SBA-Fe(acac:salen). The N2 adsorption, and low-angle XRD characterization techniques revealed the presence of structural and textural characteristics of parent SBA-15 in SBA-Fe(acac:salen) heterogeneous catalyst. The anchored acetylacetonate and salen moieties have been resolved by CHNS elemental analysis, TGA and FT-IR. The X-ray photoelectron spectroscopic analysis unveiled the existence of Fe3+ species in SBA-Fe(acac:salen) heterogeneous catalyst. The SBA-Fe(acac:salen) catalyst exhibited a overwhelming performance in activating the aliphatic CC bond of styrene and its derivatives towards the transformation of corresponding aldehydes selectively through the oxidative cleavage in the presence of aqueous 30% H2O2 at room temperature. The high performance of this catalyst is due to isolated Fe3+ species on the surfaces of hexagonally ordered mesoporous silica SBA-15 with optimal coordination environments with two different coordinating ligands.

Graphical abstractFe(III) complex composed of both acetylacetonate and salen ligands has been anchored on mesoporous SBA-15 and found that this new heterogeneous catalyst is highly active and selective at room temperature to convert CC bond of styrene into benzaldehyde.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Synthesis of Fe(III) complex anchored onto SBA-15 has great potential. ► This catalyst is highly active towards oxidative cleavage of CC bond of styrenes. ► High selectivity is due to isolated distribution of Fe(III) complex on SBA-15.