In a recent post I showed how to:
In the above video I take that one step further and show you how to import this template into a completely different site collection. This could also be in a separate unique Office 365 tenant if desired.
The process is basically to create a template, including the content if desired, from the source library. You then download the template that this creates and upload to the destination Site Template Gallery. Once there you can create a new library based on this template. When you create the new library it should also contain the content from the source location if you selected that initially.
This is a quick way to not only copy the structure of a library from one location to another, also potentially the content.