Internal electric field engineering regulated ionic liquid-functionalized h-BN/g-C3N4 heterojunctions for the solvent-free direct oxidation of cyclohexane to adipic acid

The highly selective and direct oxidation of cyclohexane to adipic acid (AA) using molecular oxygen under solvent-free conditions represents a “dream reaction” in industrial catalysis, yet is severely hampered by the inherent chemical inertness of C-H bond and the challenging activation of O 2 . Addressing this grand challenge, we report a non-metal heterointerface engineering strategy to construct an advanced B/F-doped h-BN/g-C 3 N 4 heterojunction catalyst (known as BN/CN-BF 4 ) via a facile synergistic ultrasonication and thermal treatment utilizing the ionic liquid. The resulting BN/CN-BF 4 exhibits a powerfully ability to regulate interfacial electronic microenvironment, as evidenced by spectroscopic, electrochemical analysis, and DFT calculations, which reveal a type-II staggered band alignment and an internal electric field (IEF) formation across the heterojunction. This precisely engineered heterointerface achieved a remarkable breakthrough in catalytic performance, yielding a high cyclohexane conversion of 18.8% with an unprecedented selectivity for AA reaching 51.3% (a significant advancement over the typical 3%-5% conversion) in solvent-free system. Mechanistic investigations established a multi-step synergistic catalytic mechanism that B-N sites and H-bonding facilitate the initial C-H bond adsorption and activation; simultaneously, the IEF-driven directional electron transfer and C-F bond formation significantly accelerate the activation of O 2 to generate highly reactive oxygen species, steering the reaction pathway directly towards the terminal product, adipic acid. This work provides a novel strategy for enhancing industrial selective oxidation by manipulating the interfacial electronic microenvironment with IEF, offering a promising route for advanced solvent-free and metal-free selective oxidation catalysts.