For the N-fluoropyridinium triflate (1) catalysed aziridine synthesis, all density functional theory (DFT) calculations were performed using Gaussian 16 . Whilst the M06-2X 25 functional and a mixed basis set 6-31G (d,p) 26 + LANL2DZ (I) 27 was used for geometry optimizations and frequency calculations. Additionally, we employed the SMD implicit solvation model to account for the solvation effects of dichloromethane. Frequency computations verified the optimized geometries as either minima (zero imaginary frequencies) or transition structures (a single imaginary frequency) at the same theoretical level. More accurate electronic energies were obtained by single-point energy calculations at the ωB97X-D 29 /[6-311+G(2d,p) 30 + SDD (I) 31 ]-SMD(CH2Cl2) level of theory. Grimme's quasi-RRHO correction for the frequencies that are below 100 cm -1 and concentration correction from 1 atm to 1 mol L -1 were implemented by Shermo . The geometries were generated using CYLview . The non-covalent interactions analysis of CP1 were generated by Multiwfn 36 and Pymol .