Boosting Methanol-Mediated CO2 Hydrogenation into Aromatics by Synergistically Tailoring Oxygen Vacancy and Acid Site Properties of Multifunctional Catalyst

Even though the direct hydrogenation of CO2 into aromatics has been realized via a methanol-mediated pathway and multifunctional catalyst, few works have been focused on the simultaneously rational design of each component in multifunctional catalyst to improve the performance. Also, the structure-function relationship between aromatics synthesis performance and the different catalytic components (reducible metal oxide and acidic zeolite) has been rarely investigated. Herein, we increase the oxygen vacancy (O-v) density in reducible Cr2O3 by sequential carbonization and oxidation (SCO) treatments of Cr-based metal-organic frameworks. Thanks to the enriched O-v, Cr2O3-based catalyst affords high methanol selectivity of 98.1 % (without CO) at a CO2 conversion of 16.8 % under high reaction temperature (350 degrees C). Furthermore, after combining with the acidic zeolite H-ZSM-5, the multifunctional catalyst realizes the direct conversion of CO2 into aromatics with conversion and selectivity as high as 25.4 % and 80.1 % (without CO), respectively. The property of acid site in H-ZSM-5, especially the Al species that located at the intersection of straight and sinusoidal channels, plays a vital role in enhancing the aromatics selectivity, which can be precisely controlled by varying the hydrothermal synthesis conditions. Our work provides a synergistic strategy to boost the aromatics synthesis performance from CO2 hydrogenation.

Automated summary

In this study, the oxygen vacancy density in reducible Cr2O3 was increased by sequential carbonization and oxidation treatments, leading to high methanol selectivity of 98.1% in the direct hydrogenation of CO2 into aromatics at high temperature. Furthermore, by combining with acidic zeolite H-ZSM-5, the multifunctional catalyst achieved high conversion and selectivity of 25.4% and 80.1% (without CO) in the conversion of CO2 into aromatics. The acid site property in H-ZSM-5, especially the Al species located at the intersection of straight and sinusoidal channels, played a crucial role in enhancing aromatics selectivity, which could be controlled by varying the hydrothermal synthesis conditions. This work provides a synergistic strategy for improving the synthesis performance of aromatics from CO2 hydrogenation.