If you are doing this for printing purposes, don't. Instead, when you export the PDF, choose to export "All Pages" instead of "All Spreads".
This will do what you want at the time of export so that the design file can be kept in the generally more useful facing pages mode.
If you do need to split them in the Publisher file for some reason, I don't believe this is currently possible without some added manual work. You would need to find all of the objects that span across the spreads and manually copy them from whichever side they wind up on to the side they were missing from.