Is it possible to genetically alter human beings to see parts of the infrared?
Our heads are warm, so the receptors that react to infrared radiation would be set off constantly by ambient radiation, not just radiation that comes in through the eye.  Note that the animals that do see infrared are cold blooded.

So it would be a massive genetic engineering project to get working infrared vision, to either make human heads be room temperature, or to thermally insulate eyeballs from the surrounding tissue.