Hello.
I'm not a master in russian but the difference between the words is clear for me (depends on context though).
I agree with the others but have something to add:

Знания (познания) - something that you have already got - knowledges (знание; познание (more rarely) singular - knowledge).

Познание - this is a process of getting knowledges (learning, comprehension, often used in philosophy). The verb is познать, познавать (cognize, perceive are the most suitable words in English in my opinion). Like gerunds in English - познавать or познать - познание (process). Познавать мир (себя, etc.) - познание мира.