Possible explanation of primordial ${}^7$Li deficit

A reduction mechanism of the theoretically predicted excessive abundance of ${}^7$Li via baryons evaporated by primordial black holes is suggested. It is shown that the fraction of ${}^7$Li with respect to the number density of baryons can be diminished down to the observed value via the process of ${}^7$Li transformation by neutron capture. The created in this process ${}^8$Li or ${}^8$Be quickly decay into a pair of ${}^4$He nuclei.