How to repair a freon leak from a puncture ?

The only way to prpoerly repair is to remove the freon, braze the hole and recharge.

There are repair kits available at almost any appliance or HVAC parts store, but you need to clean the area really well, sand it, and have a tiny amount of vacuum temporarily for the epoxy to stick. Even then it's an iffy type fix; brazing it is better, but takes a lot of skill to do and if you get the aluminum just slightly too hot you will have a big hole that cannot be fixed. One should never defrost with an icepick or knife.