Urea synthesis via thermal catalytic coupling of N2 with CO2 on singly dispersed Co1Ru3 bimetallic clusters: a theoretical perspective
The industrial production of urea through the integrated Haber–Bosch and Bosch–Meiser processes involves high energy consumption and significant CO2 emissions. Given the persistent technical challenges inherent in direct electrocatalytic methods, catalytic systems that enable the thermal coupling of N2 and CO2 under mild conditions represent a promising and sustainable approach to urea synthesis. Herein, we designed MXene-based bimetallic single-cluster catalysts, M1Ru3@Mo2CO2, in which the M1Ru3 cluster is stably anchored on the Mo2CO2 support. Using density functional theory calculations, we systematically evaluated the structural stability and adsorption capabilities of 3d transition metal variants (M = Sc to Zn) toward N2, CO2, and H2. The results demonstrate that Co1Ru3@Mo2CO2 exhibits excellent thermodynamic stability and enables the synergistic activation of N2, CO2, and H2, fulfilling the prerequisite conditions for catalyzing the direct coupling of N2 and CO2 to form urea. Further analysis reveals that Co1Ru3@Mo2CO2 efficiently promotes the direct thermal coupling of N–C into urea under mild conditions via the associative pathway, with the rate-determining step corresponding to the conversion of *NHNH2 → *NH2NH2 with the low energy barrier of 1.16 eV. Under realistic conditions of 780 K and 29 bar, the calculated turnover frequency reaches 1.01 × 10−3 s−1 site−1. The high catalytic performance arises from the ability of the Co1Ru3 bimetallic cluster to precisely modulate charge transfer between support and reaction intermediates. Moreover, the in situ generated NH2 species acts as an autocatalyst for CO2 hydrogenation, while the cluster selectively enhances the electrophilicity of the *CO intermediate, thereby facilitating the nucleophilic attack by *NH2 and ensuring efficient C–N bond formation. The finding of the outstanding performance of Co1Ru3@Mo2CO2 single cluster catalysts could bypass the energy-intensive NH3 synthesis step, reduce overall energy demand, and remain compatible with existing urea production infrastructure, thereby offering significant scientific and technological significance.