Question

On what grounds, can a member be suspended or expelled from the UNO?

Answer 1

A member of the United Nations, against whom enforcement action has been taken by the Security Council, can be suspended from exercising the rights and privileges of the United Nations by General Assembly on recommendation of the Security Council. This is provided in the Article 5 of the Charter.
According to Article 6 of the Charter a member persistently violating the principles of the Charter can be expelled from the United Nations by the General Assembly on recommendation of the Security Council.