We have investigated the [2+1] cycloaddition reactions of carbenes with the isolated C=C units of (n, 0) BC2N nanotubes, n =3, 4 and 5. The CHF carbene was considered to investigate whether replacing one of the fluorine atoms of difluoro carbene (CF2) with hydrogen leads to less repulsion between the carbenes. The existence of hydrogen bondings have been indicated in (n, 0)/(CHF)2n based on NBO analysis. Reaction energies of (n, 0)/(CH2)2n and (n, 0)/(CHF)2n with fully functionalized belts are found to be negative. This can be due to the counteraction of the cyclopropane ring strain formed on the tube and the interactions between carbenes, such that replacing hydrogens of these carbenes with fluorine ones leads to the endothermic character of the reactions. Also, removing half of the carbenes, eliminates repulsion between the carbenes but increases the ring strain, leads to endothermic character of Er.