I recently interviewed with Software Company X, declined their job offer, and left the process on good terms. They were not quite the right fit for me at this point in my career, but I could potentially see myself contacting them again down the road. Now, I have a close friend who has applied to several positions at X and has not gotten any response. The friend has asked me if I will put in a good word for him with my recruiter (who is internal to Company X).
Obviously, I would like to do a nice favor for my friend, since he's very excited about this company. But I have some hangups:
In general, I don't know whether it is considered unprofessional to refer a friend to a company where I don't work. Is this a faux pas that would somehow damage my relationship with Company X?
While I went to school with this friend (our majors were tangentially related to our current jobs) and can vouch for him as a generally smart and talented person, we went (relatively) separate ways in our careers and I have not actually worked with him professionally at any point. Also I don't really have an understanding of what the company is looking for in the roles he is interested in. So, I can't genuinely vouch for how good a fit he is for these positions.
So all in all, I would like to do a nice thing for my friend, but I am hesitant to full-on tell the recruiter that she should (re?)consider his resume. Given this information, would it be potentially harmful to my relationship with Company X to refer my friend?
Edit
I think this isn't quite a duplicate of this question because of several complicating variables:
My friend solicited this favor --- it wasn't my idea.
My friend has already sent in several job applications to this company which have not gotten responses.
- It is a personal friend, not a previous coworker.