Yeah as others have mentioned, this is a surefire way to find corruption in new an exciting ways.

How do you determine IQ?

No matter how you answer this question you open yourself up to different methods of corruption, as well as coincidental prejudice.

Is your test based on things only taught in college? Boom! now poor people cant vote.

Is your test based on common knowledge about the world? Boom, people outside of your bubble cant vote.

Also who runs the tests? Who oversees the questions asked? How do you make testing accessible for people with physical impairments? How do you ensure a proper testing environment? Each and every step has a way to inject corruption, and the kind of corruption that grows, since once you start limiting the voting pool u can limit it in a way that allows your brand of corruption to grow.

Its unfortunately not feasible.