Xylene Synthesis Through Tandem CO₂ Hydrogenation and Toluene Methylation Over a Composite ZnZrO Zeolite Catalyst

Selective synthesis of specific value-added aromatics from CO₂ hydrogenation is of paramount interest for mitigating energy and climate problems caused by CO₂ emission. Herein, we report a highly active composite catalyst of ZnZrO and HZSM-5 (ZZO/Z5-SG) for xylene synthesis from CO₂ hydrogenation via a coupling reaction in the presence of toluene, achieving a xylene selectivity of 86.5 % with CO₂ conversion of 10.5 %. A remarkably high space time yield of xylene could reach 215 mg g_cat ^-1  h^-1 , surpassing most reported catalysts for CO₂ hydrogenation. The enhanced performance of ZZO/Z5-SG could be due to high dispersion and abundant oxygen vacancies of the ZZO component for CO₂ adsorption, more feasible hydrogen activation and transfer due to the close interaction between the two components, and enhanced stability of the formate intermediate. The consumption of methoxy and methanol from the deep hydrogenation of formate by introduced toluene also propels an oriented conversion of CO₂ .