Enhanced Acid-Base Synergistic Effect of CuxFe0.5Ce0.5 Metal Oxide Composite for Highly Efficient Synthesis of N,N’-Diphenylurea from CO2 and Aniline

Abstract

The development of highly active catalysts for the direct synthesis of N,N’-diphenylurea (DPU) from CO₂ and aniline is crucial yet has faced significant challenges. This study introduces a metal oxide composite catalyst, Cu_xFe_0.5Ce_0.5, synthesized via a one-step co-precipitation method. This catalyst features both acidic and basic active sites that synergistically catalyze the conversion of CO₂ and aniline into DPU with high efficiency. It achieved an aniline conversion rate of up to 33.0% and an exceptional DPU selectivity of 99.9%. Comprehensive characterizations confirmed that the catalyst possesses well-defined morphology, controlled size, optimized pore structure, and robust acid-base properties, along with abundant oxygen vacancies. Specifically, CuFe components function as Lewis base sites, effectively activating CO₂ molecules, while Ce^3+/4+ species serve as Lewis acid sites, facilitating the adsorption and activation of aniline to form key intermediates. Importantly, the presence of oxygen vacancies enhances electronic interactions between CeO₂ and metals, increasing metal electron density and providing critical active sites for CO₂ adsorption and activation, thus promoting the efficient catalytic reaction progression. Moreover, the catalyst demonstrates excellent reusability, maintaining approximately 95% of its catalytic efficiency after five cycles. This work provides an innovative approach to developing efficient catalysts for the valorization of CO₂ into higher value-added chemicals.