It was mentioned in my course book under "Characteristics of physisorption" that:
- Lack of specificity: An adsorbent does not show any preference for a particular gas as the van der Waal's forces are universal.
- Nature of adsorbate: In general an easily liquefiable gas is more readily adsorbed as it's critical temperature is higher as van der Waal's forces are stronger near critical temperature.
Aren't these two points contradictory? If not then please explain.