A butyl rubber (or latex for that matter) tube is not an impermeable membrane, i.e. it has lots of little holes that allow gas to pass out of it. For CO2, the gas dissolves in the rubber and, like a wet cardboard...sorry...corrugated fiber board box, the CO2 seeps out. Basically, it just passes through.

However the tube isn't going to hold any gas forever. For the other gasses, the holes and channels that make up the box just take a little longer to get through. Kinda like when you put oil in that box. The oil will eventually seep out but it will take longer because it doesn't dissolve in the box. The loss of pressure in the tube is driven by the Principle of Le Chatelier. In a nutshell, Le Chatelier's principle says that any system not at equilibrium will try to get to equilibrium. As my old chemistry teacher put it, "Every thing goes the way the wind blows." The tube has channels and holes that allow gases to pass in both directions. Gas can go in and go out, albeit slowly. Since the pressure in the tube is higher than the pressure outside the tube, the gas tends to go out rather than in, i.e. that's the way the wind is blowing

Put any gas in the tube under pressure and it's going to find a way out. Helium and CO2 will find a way out rather quickly (on the order of hours), air (78% N2 and 19% O2) will find a way out in a matter of days. N2 by itself is going to have pretty much the same rate. O2...well, I don't know but putting pure O2, a oxidizable organic polymer, and heat together is likely not a combination I'm going to test any time soon I think I'll stay away from methane for the same reason. Boomba! Boomba!

Other exotic gases might take less time or more time than air. It's kind of hard to predict. But the problem with any gas is that you'll have to fill the tire from time to time. Exotics are exotic because they are rare and difficult to isolate. Therefore they cost more. And the benefit is probably pretty low. Air and a pump are still pretty economical.

Now if you want to do something, design a better tube. Mylar is far less permeable than rubber. It'd hold gas for a very long time but it has no puncture resistance and no...zero...nada...zilch elasticity. Urethane was tried for a while and it works...sorta. It's not as elastic as rubber, it holds pressure slightly better, it has better puncture resistance than mylar but less - way less - than rubber, and it is a royal pain to patch...and costs around 5 times as much as rubber. Not a whole lot of plusses