Najis Things

If the father of the child is Buddhist, and his mother is a Muslim, will the mother’s religion allow the child to be considered Muslim and tahir?

The marriage is void in the said case since it is prohibited for a Muslim woman to marry a non-Muslim man. If she knew that her marriage was invalid, then the child is not considered tahir. If she was unaware of the invalidity of her marriage, then the child is considered tahir.