Iron grafted over mesoporous silica (8 wt %Fe/SBA‐15) is a sustainable, efficient heterogeneous iron catalyst for direct arylation of biphenyl methane C(sp3)−H and benzene C(sp2)−H bonds. The selective extraction deposition (SED) technique was adopted to graft iron easily over the mesoporous support SBA‐15 by using LaFeO3 as an iron precursor. The synthesized catalyst has been characterized by EPR spectroscopy, diffuse reflectance UV/Vis spectroscopy, and temperature programmed reduction (TPR) analysis to understand the coordination environment and state of oxidic iron species grafted over the mesoporous SBA‐15. TPR results confirm the presence of isolated, clustered, oligomeric oxidic iron species in the catalyst. The adopted SED technique is highly successful for grafting 8 wt % iron into the mesopores of SBA‐15 without forming iron oxide particles. Unlike homogeneous iron, the 8 wt %Fe/SBA‐15 catalyst does not need support from an electron‐withdrawing group and additives to carry out arylation of benzene and could be successfully recycled five times.
Magnetite (FeO) nanoparticle-encapsulated mesoporous carbon nanocomposite was fabricated from Fe-based metal-organic framework (MOF) (MIL-102) through carbonization. It was found that Fe-based MOF (MIL-102) is a potential precursor for the fabrication of hexagonal mesoporous carbon nanodisk functionalized with FeO nanoparticles. The obtained nanocomposite was characterized by XRD, FT-IR, N adsorption and desorption, FE-SEM and HRTEM techniques. As a Fenton-like solid catalyst for phenol degradation, FeO nanoparticle-encapsulated mesoporous carbon showed greater catalytic activity for the production of hydroxyl radical from the decomposition of HO and it accomplished 100% phenol and 82% total organic carbon (TOC) conversion, within 120 min of reaction. This enhanced catalytic performance was due to confined access for the pollutant to the iron oxide nanoparticles provided by mesopores in carbon shell. Bare FeO nanodisk shows poor catalytic performance in the degradation of phenol, and it obviously reveals the significance of the mesoporous carbon support for iron oxide nanoparticles.
AlSBA-15 catalysts possessing Brønsted acid and Lewis acid–base bifunctionalities catalyze the direct arylation of benzyl alcohols to diarylmethanes with an 85% product yield through C–O bond activation.
2–8 wt % iron has been grafted over SBA‐15 and 10 wt % alumina grafted SBA‐15 (AlSBA‐15) through selective extraction deposition technique using LaFeO3 as iron precursor in acidic solution. DRS‐UV spectra confirmed the presence of iron as isolated Fe(III), Fe(III)‐clusters and amorphous FeOx oligomers. SEM‐EDX mapping, FT‐IR, XPS, HR‐TEM and 27Al MAS NMR characterisation results confirmed that iron grafted over AlSBA‐15 preferentially reside on the alumina. The donor‐acceptor interaction of grafted iron ions with alumina atoms displaying Lewis acid properties stabilized iron at higher oxidation state Fe(III+δ). This increased the BE of Fe2p electrons (XPS) and shifted the temperature of iron reduction in 2–8 wt %Fe/AlSBA‐15 materials to higher value (600 °C) compared with Fe/SBA‐15 (H2‐TPR). In arylation of benzene, 8 wt %Fe/AlSBA‐15 demonstrated excellent redox catalytic activity with TOF close to homogeneous catalyst and 82 % biphenyl yield. The catalyst demonstrated consistent catalytic performance for 7 cycles.
24 wt% of iron has been successfully grafted as amorphous iron oxide over mesoporous channels of SBA‐15 and 10 wt% alumina coated SBA‐15 (AlSBA‐15) using selective extraction deposition (SED) technique. The synthesized materials have been characterized using XRD, N2 adsorption studies, SEM‐EDS, 27Al MAS NMR, XPS, H2‐TPR, and HR‐TEM techniques. 27Al MAS NMR and XPS characterization results revealed that iron has been preferentially grafted over alumina. The increased binding energy of the Fe2p electron (XPS) in the 24wt %Fe/AlSBA‐15 confirms the existence of strong donor‐acceptor interaction between grafted iron oxide and an alumina support. In TPR studies, unlike silica support, AlSBA‐15 tuned the reduction property of various grafted oxidic iron species, which is evidenced by shifting of iron reduction peak to a high temperature of 436 °C. In the destruction of 200 ppm of phenol 24wt %Fe/AlSBA‐15 catalyst demonstrated 100% phenol conversion and 86% TOC removal with 0.4 ppm (0.1%) iron leaching within 30 minutes of reaction. 24wt %Fe/SBA‐15 catalyst also exhibited similar performance however, leaching of iron was found to be up to 20 ppm (8%). The 24wt %Fe/AlSBA‐15 catalyst was recycled successfully five times without loss in the catalytic activity and stability.
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