Is there a punishment for holding the Qur'an in a unclean state like after having sex or for a woman after giving birth I've not seen anything about it
In the name of Allah. The Quran is material, but consider any material touched. Consider the future of other users. Paper can absorb the stain and how long would that stain remain? I imagine that its possible that years later one could while reading it seeing the stain and think of the stain instead of Allah. Therefore because it is good that the thought remains upon Allah become clean and respect your others then use any material shared of by others (including the Quran).
The punishment is like this, whoever does make anything dirty should make it clean, and if needing help ask the others with the help of Allah.