First, do try manual technique:
Just right-click any folder in one PST and then select "Move folder" to move it to another PST. If you wish to do this by date, use the unique Export feature of Outlook, and click the Filter button to select the date range. Once you have added the items to the new PST, delete them from the old PST location, because they are copied, but it still works fine.
Or else you can use the third party splitter Like PST Split software
, Being a professional software, it provides unlimited features which not only split your large PST Files but do provide different option to split PST Files.