@f604b7a1 It depends on what part of the infrared range we're talking about. In the so-called mid-infrared, the absorption/emission of our atmosphere is more prominent. The ELT will have an instrument called METIS that will observe at these wavelengths. Besides taking very sharp images it can also take very high resolution spectra. This complements JWST, which focuses more on sensitivity. You can find more info here, including a short movie about METIS: https://elt.eso.org/instrument/METIS/ 

 @f604b7a1 At somewhat shorter infrared wavelengths – what we call the near-infrared – these atmospheric effects are milder. Other ELT instruments will observe at these wavelengths, like MICADO: https://elt.eso.org/instrument/MICADO/