You mean if
energy cannot escape, neither can matter.
About the energy inside a black hole:
If matter turns into energy inside a black hole, and
if a photon does
not have a mass, the black hole will in the end lose so much mass that the energy and matter will be able to escape.
However, if the black hole does not change the form of the matter into energy, it may be trapped inside it forever.
But, if the matter is very hot, I assume some of it will turn into photons, so, that must mean black holes will lose their matter in the end.
Correct me if I'm wrong.