If you want to disconnect your domain from a collection, follow the steps below.
On the My Publications page, open the collection you wish and click the Action button in the upper-right corner.
Note: You can also navigate to Domain section by clicking the URL in the upper-left corner, and then clicking Domain settings.
Go to the Viewer Settings
Scroll down to find the Domain Connect and disconnect your domain
Once done click Save or Save and Close button
Now you know how to disconnect your domain from a collection.
Joomag help: Learn how to link your domain name to a collection.