Look up Carnot efficiency. The maximum amount of work you can theoretically extract depends only on a temperature difference. For a datacenter running chips at 100C into ambient air at 60F, it's about 25%. So even with perfect capture, you are guaranteed to lose 3/4 of your input energy to the datacenter as heat anyway.

For comparison, an IC engine has a Carnot efficiency of something like 80% on paper, but the reality you get is only 20-30%