That would be none - IR is a very broad range and the EM spectrum is also extremely broad.
To absorb all IR and none of the rest is a tall order.
Perhaps you are thinking of an infra-red cutoff filter?
An absorbtive filter would be glass, though you can also use thin-film techniques I guess.
Commercial flter manufacturers are cagey about exactly how they make their glass, however, practically everything absorbs some infra-red.
Example: http://lofi.forum.physorg.com/IR-Cutoff-filter-*_88.html [Broken] of different materials.
You would really be better off to find something that reflects the IR, or most of it, like aluminum. Anything that would absorb IR, would have to do something with all that heat.
Some of the heat would no doubt be re-transmitted into the space you are trying to protect. You might be able to do some sort of clever dodge where you have grating strips on a window, and secondary reflectors positioned only in the visible portion of the spectrum enters the space. I have no idea how broad a range that would cover. Something like the above would let light in, but would distort looking out the window.(rainbow effect)