This paper investigates the formation of primordial black holes (PBHs) from the collapse of self-enclosed axion domain walls in the context of axion cosmology. The QCD axion, a candidate for dark matter, can solve the Strong CP Problem and may form domain walls if the axion decay constant $ f_a $ is below the inflationary reheating temperature. These walls can collapse into PBHs if they are not attached to cosmic strings. The authors study the number density, size distribution, and dynamics of these walls using a combination of semi-analytic and numerical methods. They find that axion models with high $ f_a $ values, such as those in early matter-dominated cosmologies, can produce PBHs potentially observable via future gravitational lensing surveys. The paper also discusses the conditions for PBH formation, including the compression of energy into a Schwarzschild radius, and the suppression of collapse due to angular momentum and collisions with other defects. The results show that PBHs can form when walls become dynamical, typically after the string-wall network collapses. The authors calculate the PBH abundance and discuss its detectability through gravitational lensing. They also compare their results with other models and note that their approach provides a reliable estimate of the present-day PBH energy density in a fully post-inflationary scenario. The study highlights the importance of domain wall dynamics, including their superhorizon expansion and subhorizon collapse, in determining PBH formation. The paper concludes that PBHs can constitute a significant fraction of dark matter in certain cosmological models.This paper investigates the formation of primordial black holes (PBHs) from the collapse of self-enclosed axion domain walls in the context of axion cosmology. The QCD axion, a candidate for dark matter, can solve the Strong CP Problem and may form domain walls if the axion decay constant $ f_a $ is below the inflationary reheating temperature. These walls can collapse into PBHs if they are not attached to cosmic strings. The authors study the number density, size distribution, and dynamics of these walls using a combination of semi-analytic and numerical methods. They find that axion models with high $ f_a $ values, such as those in early matter-dominated cosmologies, can produce PBHs potentially observable via future gravitational lensing surveys. The paper also discusses the conditions for PBH formation, including the compression of energy into a Schwarzschild radius, and the suppression of collapse due to angular momentum and collisions with other defects. The results show that PBHs can form when walls become dynamical, typically after the string-wall network collapses. The authors calculate the PBH abundance and discuss its detectability through gravitational lensing. They also compare their results with other models and note that their approach provides a reliable estimate of the present-day PBH energy density in a fully post-inflationary scenario. The study highlights the importance of domain wall dynamics, including their superhorizon expansion and subhorizon collapse, in determining PBH formation. The paper concludes that PBHs can constitute a significant fraction of dark matter in certain cosmological models.