Alumina as Solid‐State Ligand in Enhancing the Redox Catalytic Property of Iron Oxide Grafted AlSBA‐15 towards Arylation of Arene

Abstract

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.

Enhanced Stability of Abundant Amorphous Iron (III) oxide Grafted AlSBA‐15 as Highly Efficient Heterogeneous Fenton Catalyst for the Destruction of Phenol

“…XPS analysis was carried out to scrutinize the coordination of the Fe and Al existing in 24wt %Fe/SBA‐15 and 24wt %Fe/AlSBA‐15 (Figure ). The deconvoluted Fe2p 3/2 spectra of 24wt %Fe/SBA‐15 exhibits two peaks at binding energy values 710.5 eV and 712.1 eV correspond to Fe 3+ in ground state and iron oxide oligomer, respectively . The significant shift in binding energy values to 711.5 eV and 713.4 eV were observed after insertion of Al in 24wt %Fe/AlSBA‐15.…”

“…The Lewis acid acceptor nature of Al establish a donor‐acceptor interaction between Fe and Al ions and thereby increases the binding energy value of Fe ions grafted over AlSBA‐15 compared to SBA‐15. In Figure c the deconvoluted Al2p spectra of 24wt %Fe/AlSBA‐15 exhibits three distinct peaks at binding energy values 73.5 eV, 74.41 eV and 75.0 eV confirm the existence of three interfaces corresponds to Al‐O−Fe, Al‐O−Si and Al‐O−Al linkage . XPS observation reinforces the 27 Al MAS NMR inference that oxidic iron species are preferentially grafted over the alumina coated over the mesoporous support SBA‐15.…”

“…8wt %Fe/SBA‐15 demonstrated excellent redox catalytic activity towards arylation of biphenyl methane and benzene involving the C(sp3)‐H and C(sp2)‐H activation, respectively . To our delight, in the arylation of benzene, 8 wt% Fe grafted over alumina coated SBA‐15 (8wt %Fe/AlSBA‐15) exhibited three times more redox catalytic activity than 8wt %Fe/SBA‐15 with turn over frequency close to the homogeneous iron catalyst . In the above study, we identified that alumina played a critical role through its Lewis acid property to tune the redox catalytic property of the grafted iron oxide species.…”