There's no option to block sites on chrome mobile.... BUT I have an method that you can use to block certain websites.
1. Install an app called "APPBLOCK" from the play store. This app is around 7.9 MB with over 4.4 stars of rating.
1. Install AppBlock from PlayStore
That’s it. Thiat's a three-step simple process to block websites on Chrome browser you can perform this on any Android device.