Polyoxymethylene dimethyl ethers (OMEs) emerging as green additives for soot emission suppression receive significant attention due to their similar physical properties to diesel. Herein, the transformative pathways of dimethoxymethane (DMM) and trioxane reactions for OMEs production catalyzed by [Omim]Cl/ZnCl 2 having different ZnCl 2 content were demonstrated in combination with the clarification of active species, kinetic and thermodynamic properties, and chemical nature for trioxane decomposition and subsequential formaldehyde insertion steps. The role of [Omim]Cl, which could transform to [Omim]ZnCl 3 or [Omim]Zn 2 Cl 5 under differentZnCl 2 content, laid in the formation of active zinc species and promotion of their homogeneity with reactants. The DMM chain growth, which followed the same mechanism and kinetic law, showed kinetic and thermodynamic regimes and had identical equilibrium distribution of OMEs. Only Zn 2 Cl 5 À species were active for trioxane decomposition, which was the kinetic-relevant step, while both ZnCl 3 À and Zn 2 Cl 5 À were effective for DMM chain elongation.