You could bind the catalog to specific workspaces, making them accessbile only from workspaces they are bound to.
https://docs.databricks.com/en/catalogs/binding.html

In your example:
if `my_catalog_2` is bound to `my_workspace_2` a user in `my_workspace_1` will not be able to access or modify objects in `my_catalog_2` even if they have permissions to do so in Unity Catalog.