How to exclude posts that already appear in the main loop, from the category loop

In my front-page I have 2 loops:

How can I remove from the second loop (specific category loop) those that already appear in the first loop (general loop)?

I know that I have to use post__not_in => array($excludeID) in my second loop, but I can’t catch all those id’s in the first loop.

Here is my code so far: