Dynamic Brønsted–Lewis coordination switching enables self-repairing Beckmann catalysis

The intrinsic tension among strong Brønsted acidity, Lewis acid assistance, and catalyst stability in homogeneous systems fundamentally constrains the efficiency and recyclability of Beckmann rearrangement catalysis. In conventional dual-acid systems, static Brønsted–Lewis interactions inevitably lead to active-site passivation, acid accumulation, and irreversible deactivation, thereby severely compromising catalytic activity and reusability. Here, we report an intelligent, thermo-responsive Brønsted–Lewis dual-acid deep eutectic solvent, RDES[PEG600][CF 3 COOH] 3 [InCl 3 ] 0.1 , constructed on a dynamic coordination-switching strategy. By enabling reversible switching of coordination sites and autonomous regeneration of active centers, this system successfully overcomes the above-mentioned limitations. Trace amounts of In 3+ not only introduce spatially well-dispersed Lewis acid sites but also induce a controllable perturbation of the hydrogen-bonding network, thereby promoting reversible oxygen-to-nitrogen (O → N) coordination switching during the catalytic cycle. This dynamic synergy effectively prevents acid-site saturation and enables a temperature-driven homogeneous reaction/heterogeneous separation process. Experimentally, under reaction conditions of 100 °C, cyclohexanone oxime conversion reaches 99.7% with an ε-caprolactam selectivity of 99.3%, accompanied by a pronounced reduction in the apparent activation energy to 21.0 kJ·mol −1 . Combined density functional theory calculations, molecular dynamics simulations, and electronic structure analyses reveal a previously unrecognized catalytic state-evolution mechanism, in which Lewis acid coordination switching is precisely synchronized with proton transfer, rearrangement chemistry, and catalyst self-repair. Beyond providing a new paradigm for the design of stimuli-responsive polyacid catalytic systems, this work establishes a theoretical foundation for the development of multifunctional liquid-phase catalysis extending well beyond the Beckmann rearrangement.