The direct synthesis of dimethyl carbonate (DMC) from CO 2 and methanol (MeOH) offers a promising route to address both energy sustainability and climate concerns, yet its industrialization remains hampered by insufficient catalytic efficiency. Herein, we report a three-dimensional (3D) heart-shaped CeO 2 (CeO 2 -180), assembled from ultrafine nanoparticles via optimized hydrothermal synthesis at 180 °C. This unique morphology generates abundant grain boundaries (GBs) and an interconnected pore network – clearly resolved by HR-TEM and AC-TEM – which together provide a high density of highly accessible active sites. Structural and surface analyses reveal that CeO 2 -180 possesses significantly enriched Ce 3+ (EELS, Ce 3d XPS) and oxygen vacancies (OVs, O 1s XPS, EPR) compared to counterparts synthesized at lower hydrothermal temperatures. These defects stabilize a greater population of medium-strength acid–base sites, creating a favorable surface environment for DMC formation. As a result, CeO 2 -180 delivers an exceptional DMC formation rate of 28.7 mmol·g –1 ·h –1 under optimized conditions (160 °C, 3 MPa CO 2, 2 h) – the highest value yet reported under comparable conditions. The structural advantages – particularly the high density of GBs – also contribute to a markedly faster reaction rate relative to CeO 2 -120. Moreover, the catalyst exhibits outstanding operational stability, retaining 94% of its initial activity (27.0 mmol·g –1 ·h –1 ) after five consecutive runs. In situ infrared spectroscopy further elucidates the reaction pathway over CeO 2 -180, confirming the critical role of OVs and GBs. By integrating morphology engineering with defect chemistry, this work establishes a rational design strategy for high-performance CeO 2 -based catalysts and provides new insights into the construction of 3D architectures for CO 2 conversion.
Xia et al. (Mon,) studied this question.