Single-atom Pd bridge on C60 enhancing Pd nanoclusters: Synergistic catalysis for highly selective cyclopropanation

Synergistic Pd 1 and Pd NC on C 60 enable highly efficient alkene cyclopropanation. • Competitive electron effects from Pd SAs reduced the valence of Pd NCs. • C 60 served as electron buffer stabilized multiple reaction intermediates. • Competitive electron effects lower the reductive elimination energy barrier. • Product shows higher density and energy than JP-10 for aerospace fuels. Cyclopropane structure, possessing the highest intrinsic ring-strain, are pivotal structural motifs in biomedicines and energy materials. However, their precise and efficient synthesis remains a persistent challenge, primarily due to insufficient catalytic activities that hamper the formation of key metal carbenoid intermediates and lead to the low selectivity. Herein, we report a synergistic C 60 /Pd 1+NC catalyst, uniquely integrating Pd single atoms (SAs) and nanoclusters (NCs) on the C 60 , for the highly efficient and selective cyclopropanation of alkenes. The C 60 /Pd 1+NC catalyst significantly outperforms its single-component counterparts (C 60 /Pd 1 and C 60 /Pd NC ), achieving exceptional alkene conversion (99.6%) and selectivity (86.0%). Comprehensive XAFS analysis and DFT calculations elucidated Pd C bonds were formed between Pd and the C 60 framework. The competitive electron effect from Pd SAs reduced the valence of Pd NCs to promote the dissociation of CH 2 N 2 . C 60 served as electron buffer stabilized multiple reaction intermediates. These two aspects decreased the energy barrier of reductive elimination of palladocyclobutane (31.5 → 25.6 kcal/mol), which dramatically enabled the highly efficient cyclopropanation. The obtained diadduct has the higher density (0.99 g/cm 3 ) and volumetric calorific value (42.69 MJ/L) than the typical JP-10, which could be applied for high-energy aerospace fuel. This work not only provides a powerful catalytic strategy for constructing strained three-membered rings but also gains fundamental insights into the synergistic mechanism in hybrid single-atom/nanocluster systems.