Is donating the value of papers taken from the workplace to a mosque permissible, given that no attempt was made to return the papers?

If the paper is authorized by the employer, then there is no harm in taking it. However, if the father took it without permission, this is forbidden because it is a breach of trust (amanah), and he must be advised by explaining the religious ruling. The paper or its value must also be returned to the employer. One's responsibility (dhimmah) is not cleared by donating it as charity. It can be returned without the father's knowledge. If none of this is possible, it is hoped that donating charity for building a mosque will clear the responsibility, along with frequent seeking of forgiveness (istighfar).