  The effect of humidity on the cooperative adsorption of CO2 from air on amine
appended metal organic frameworks is studied both experimentally and
theoretically. Breakthrough experiments show that at low relative humidities
there is an anomalous induction effect, where the kinetics at short times are
slower than kinetics at long times. The induction effect gradually vanishes as
relative humidity is increased, corresponding to an increase in CO2 adsorption
rate. A new theory is proposed based on the Lattice Kinetic Theory (LKT) which
explains these experimental results. LKT is able to accurately represent the
measured data over the full range of humidities by postulating that the
presence of adsorbed water shifts the equilibrium clusters from cooperatively
bound chains to non-cooperatively bound CO2. A consequence of this transition
is that CO2 exhibits type V adsorption in dry air, and type I adsorption in
humid air.
