Four years ago I stayed for a night at the Libertel Bellechasse (7th).
Based on that experience, I would definitely recommend it to you. My room
was small but modern, comfortable and very clean. As I recall, it was
close by the Solferino metro stop. The area felt exceptionally safe
because nearby are a number of embassies, the Palais Bourbon where the
National Assembly meets and the Hotel Matignon where the Prime Minister
lives. Should you want to eat close to the hotel in the evening, there are
also a lot of restaurants along the streets that run parallel to one
another to the east of the hotel - Blvd St Germain, Rue De L'Universite,
Rue de Verneuil, Rue de Lille.
Have a great trip!