Moving website (partially) to a new domain name

Hi, the theme of my website changed from the moment when I created it. And now for let's say 1/2 of the content with good traffic the domain name is absolutely unrelated. So I am thinking of moving this content to a new related domain name by 301-redirects. Anyone done something like this before? Can you share pros and cons. May it hurt the traffic for the existing content?

I have a good domain name with my keyword matching the content in it. Also the domain is 5yo, but never used. I think it will improve the rank of the content I will create on the same topic in the future. But I am afraid to harm the traffic I already have.