Sure, here are a few examples of sentences completed with noun clauses:

1. He knows that she is coming to the party tonight.
2. He knows that the project deadline is next week.
3. He knows that his friends are planning a surprise for him.
4. He knows that the weather will be bad tomorrow.
5. He knows that his efforts will eventually pay off.
6. He knows that the answer to the problem is complicated.
7. He knows that they have already left for the trip.
8. He knows that the meeting has been rescheduled.
9. He knows that his favorite team won the match.
10. He knows that learning a new language takes time and practice.