یک فوتوکاتالیست کارآمد برای هیدروژنه کردن نیتروبنزن به آنیلین
ABSTRACT
1- Introduction
2- Computational methods
3- Results and discussion
4- Conclusions
References
ABSTRACT
The hydrogenation of nitrobenzene into aniline is one of industrially important reactions, but still remains great challenge due to the lack of highly active, chemo-selective and eco-friendly catalyst. By using extensive density functional theory (DFT) calculations, herein we predict that single Pt atom decorated g-C3N4 (Pt@g-C3N4) exhibits excellent catalytic activity and selectivity for the conversion of nitrobenzene into aniline under visible light. The overall activation energy barrier for the hydrogenation of nitrobenzene on single atom Pt@g-C3N4 catalyst is even lower than that of the bare Pt(111) surface. The dissociation of N–O bonds on single Pt atom is triggered by single hydrogen atom rather than double hydrogen atoms on the Pt(111) surface. Moreover, the Pt@g-C3N4 catalyst exhibits outstanding chemoselectivity towards the common reducible substituents, such as phenyl, –C=C, –C≡C and –CHO groups during the hydrogenation. In addition, the doped single Pt atom can significantly enhance the photoconversion efficiency by broadening the light absorption of the pristine g-C3N4 to visible light region. Our results highlight an interesting and experimentally synthesized single-atom photocatalyst (Pt@g-C3N4) for efficient hydrogenation of nitrobenzene to aniline under a sustainable and green approach.
Introduction
Hydrogenation is among the most important and challenging technological reactions in modern chemical industry [1]. The high activity and chemoselectivity are often very difficult to control especially when more than one reducible groups are present during the hydrogenation process [2, 3]. An important example is the catalytic hydrogenation of nitrobenzene into aniline, a high-value chemical raw material which can be widely used in dyes, pigments, rubber, agrochemical and pharmaceutical industry [4, 5]. Currently, the catalytic hydrogenation of nitro groups to produce anilines mainly relies on noble metal complexes catalysts, such as palladium, rhodium, ruthenium and iridium [6, 7]. Although the precious metals have the advantage of high catalytic activity, they still suffer from low selectivity and high expense. Therefore, the exploration of environmentally benign and cost effective catalysts for aniline synthesis is thus of great fundamental as well as practical interest [8–10]. Great research efforts toward improving the activity and selectivity has been made by developing a variety of catalysts: noble metal catalysts Au [9, 11, 12], AuPt [13], CoPd [14], Pd/CeO2 [2], non-noble metal catalysts Ni [15], Ni–Co as well as Ni–Fe alloys [16, 17] and so on [18–20]. However, the problem often arising is that these catalysts have to be modified by additives or combining with other metal oxides and molecules to achieve high selectivity [21–24]. In most cases, the well-chosen additives will cause environmental problems and at the same time reduce their activity [25].