Praise be to Allah.
It is not permissible for a man to forsake his wife and thus harm her, except in the case of nushooz (rebellion) and disobedience. But he is not committing a sin if he does not lie with her without intending to harm her, because the need is his and depends on his desire and he cannot control his desire at will. If he forsakes her, then he is a sinner because there should be no harming or reciprocating harm.
Allaah knows best.