Chelation-assisted and steric-controlled Mo/C catalyst through a molecular recognition strategy for value-added conversion of olefins

• A chelation-assisted and steric-controlled Mo-based catalyst was developed by a molecular recognition strategy. • Mo/TCY-CTS showed 62.7 % single-pass conversion, 95.6 % epoxide selectivity, and 88.9 % TBHP utilization efficiency. • The fluorescence probe method was employed to quantify TBHP in the reaction system for the first time. • Mo/TCY-CTS enabled the selective oxidation of olefins by enhancing the homolytic cleavage of O H bonds in TBHP via electron-coupled oxygen transfer. Against the backdrop of green and low-carbon development in the chemical industry, overcoming the challenges of insufficient anchoring sites and disordered structure in catalysts represents a critical research direction for realizing the value-added conversion of light olefins. In this study, a molybdenum-based catalyst (Mo/TCY-CTS) is designed and synthesized by anchoring molybdenum metal via a molecular recognition strategy (involving the introduction of acyl chloride, mercapto, and cyano functional groups into chitosan). The successful synthesis of this catalyst is confirmed by a series of characterization results: (1) Mo species are uniformly dispersed without agglomeration; (2) Mo(IV) and Mo(VI) coexist, with Mo(IV) serving as the key active sites; (3) the catalyst exhibits good thermal stability. In addition, the catalyst exhibits a single-pass conversion of 62.7 % for 1-hexene, a selectivity of 95.6 % for the epoxide product, and a TBHP utilization rate of 88.9 %. It also demonstrates good reusability and applicability to various olefins. For the first time, the fluorescent probe method is employed for the quantification of TBHP in the reaction system (detection limit: 0.084 mmol/L). Macroscopic thermodynamic and kinetic studies show that the reaction process of this catalytic system is endothermic and entropy-increasing, and the epoxidation reaction follows a pseudo-second-order kinetic model. This study clarifies the intrinsic mechanism whereby organic peroxides (represented by TBHP) are activated via O H bond cleavage rather than O O bond fission to form hydroxyl radicals during olefin epoxidation, providing a basis and reference for the controllable design of olefin epoxidation catalysts.