Gating effect of g-C3N4-encapsulated Pt-based catalysts for the hydrogenation and Bamberger rearrangement of nitroaromatics

C Yao and JJ Shan and J Liu and J Luo and LM Pan and JH Lyu and F Feng and LL Lin and CS Lu and Y Zheng and JG Wang and QT Wang and QF Zhang and XN Li, JOURNAL OF MATERIALS CHEMISTRY A, 12, 33606-33616 (2024).

DOI: 10.1039/d4ta07194h

Encapsulated catalysts are known for their exceptional stability; however, the encapsulation of the active sites typically leads to reduced activity. To address this issue, an effective strategy is to employ g-C3N4 (graphitic carbon nitride with a 3-s-triazine structure), which has distinctive pore channels. This material acts as a gatekeeper, allowing only small molecules such as H2 and H to pass through, while blocking Pt and larger molecules like nitrobenzene, thus preventing Pt loss. The g-C3N4 "gating effect" can enhance the dissociation of H2 on the Pt surface and greatly improve the activity. Moreover, the flow of electrons from Pt to g-C3N4 (forming a Pt-N bond) contributes to the enhancement of the H-adsorption capacity of g-C3N4, which can promote the hydrogenation of nitrobenzene adsorbed on the surface of g-C3N4. In the hydrogenation process of converting nitroaromatics to 4-aminophenol, p-methoxyphenol, and their derivatives, the key to controlling the product selectivity is the desorption of phenylhydroxylamine and its derivatives (intermediates). On the g-C3N4 surface, phenylhydroxylamine exhibited significantly reduced adsorption compared to the Pt surface, which promoted improved selectivity (selectivity increased by 29.6%). Therefore, the Pt/C@g-C3N4 catalyst disrupted the balance between the activity and selectivity in the nitroaromatic hydrogenation- rearrangement reaction, ensuring both high selectivity and stability while markedly enhancing the activity. These improvements establish favorable conditions for industrial implementation.

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