My textbook says
…easily liquefiable gases i.e. with higher critical temperatures are readily adsorbed as van der Waals' forces are stronger near the critical temperatures.
What I do understand is that at a temperature higher than the critical temperature $(T_\mathrm c)$ the gas molecules have higher kinetic energy which is why they're unable to form strong bonds.
But, what if the temperature is lower than the critical temperature? Or is my reasoning incorrect?