I don't know anything about oxygen absorbing caps, but I do know NOT to boil or even put the Coopers caps that fit on their PET bottles into very hot water. I found out the hard way on bottling day, when I steeped my caps in very hot water, and the blue plastic seals all warped badly and separated from the caps.
It was a lot of fun trying to keep the seals sanitary, while at the same time trying to unwarp them some by bending them back into shape and sticking them back into the caps. Ninety percent of the caps didn't seal on the first attempt. I had to use some regular soda bottle caps, which didn't have the same problem. They are made much better....