Robust ring-opening reaction via asymmetrically coordinated Fe single atoms scaffolded by spoke-like mesoporous carbon nanospheres.

ABSTRACT

The ability to construct metal single-atom catalysts (SACs) asymmetrically coordinated with organic heteroatoms represents an important endeavor toward developing high-performance catalysts over symmetrically coordinated counterparts. Moreover, it is of key importance in creating supporting matrix with porous architecture for situating SACs as it greatly impacts the mass diffusion and transport of electrolyte. Herein, we report the crafting of Fe single atoms with asymmetrically coordinated nitrogen (N) and phosphorus (P) atoms scaffolded by rationally designed mesoporous carbon nanospheres (MCNs) with spoke-like nanochannels for boosting ring-opening reaction of epoxide to produce an array of pharmacologically important ß-amino alcohols. Notably, interfacial defects in MCN derived from the use of sacrificial template create abundant unpaired electrons, thereby stably anchoring N and P atoms and in turn Fe atoms on MCN. Importantly, the introduction of P atom promotes the symmetry-breaking of common four N-coordinated Fe sites, resulting in the Fe-N3P sites on MCN (denoted Fe-N3P-MCN) with an asymmetric electronic configuration and thus superior catalytic capability. As such, the Fe-N3P-MCN catalysts manifest a high catalytic activity for ring-opening reaction of epoxide (97% yield) over the Fe-N3P docked on nonporous carbon surface (91%) as well as the sole Fe-N4 SACs grounded on the same MCN support (89%). Density functional theory calculations reveal that Fe-N3P SAC lowers the activation barrier for the C-O bond cleavage and the C-N bond formation, thus accelerating the ring-opening of epoxide. Our study provides fundamental and practical insights into developing advanced catalysts in a simple and controllable manner for multistep organic reactions.