Transform RGB image to *look like* Infrared
Without very much additional info, I'd presume the red channel of your camera has the highest correlation with the infrared spectrum.

Since you only have RGB and no knowledge of how that was calculated from the color sensor pixels: Take the R channel, it's as good as it gets.

The "IR effect" is for artistic purposes only. I'd doubt it has anything to do with what you see in an IR picture.

Notice that I also think you haven't tried to properly understand the physics of your problem: While I'd presume that a visible light photograph is highly correlated with a near-IR photo, that's very likely not the case for mid- and long-wavelength IR and certainly not for far infrared.

So, define your requirements better. And: ML really depends on having data. A lot of it. you might start with wrong data, but as DNN really don't lend themselves to understanding of the weights, it's very questionable that anything that you do with "emulated" data transfers to "real" IR data well.