A strong increase in the efficiency of the isotope-selective infrared laser multiphoton dissociation of 11BCl3 molecules in the natural mixture with 10BCl3 by radiation of a pulsed CO2 laser in the case of admixture of SF6 molecules, which serve as a sensitizer and simultaneously acceptors of radicals, Cl atoms formed in the dissociation of BCl3 molecules, has been detected. The yield and selectivity of dissociation of 11BCl3 molecules increase by several times and the threshold energy density for the dissociation of molecules decreases significantly in the case of their irradiation in the mixture with SF6 compared to irradiation without SF6. This property allows the single-frequency isotope-selective dissociation of 11BCl3 molecules by unfocused laser radiation at a moderate energy density (≈3–5 J/cm2), which is important and relevant for the practical implementation of the laser separation of boron isotopes.