Equilibrium sorption capacities of different probe molecules such as water, n-hexane, cyclohexane, and ammonia were used as a tool for the characterization of ALPO-11 and protonic forms of SAPO-11, CoAPO-11, and MnAPO-11. Sorption uptake at P/P-0 = 0.8 and 298 K, 2h for water, n-hexane and cyclohexane, was found to be affected by incorporating Si, Co, and Mn in ALPO-11. Generation of Bronsted acidity is expected to increase the hydrophilicity; Si, Co, and Mn analogues have exhibited such trends depending upon the extent of substitution and characteristics of the substituted cation. The amount of ammonia retained irreversibly ton account of chemisorption) during sorption measurements was found to be correlated with the intrinsic acidity possessed by ALPO-11 and its analogues. Isotherms of ammonia sorption in ALPO-11, SAPO-1I, CoAPO-11, and MnAPO-11 in the temperature range 333-483 It up to 500 Ton have been measured. The NH3 sorption capacity was also found to decrease in the order ALPO-11 > SAPO-11 > CoAPO-11 > MnAPO-11 . The sorption data were analyzed in terms of different models of sorption isotherm equations. BET, Dubinin, Langmuir, and Freundlich isotherm models could represent the sorption data satisfactorily yielding linear plots. However, Sips equation failed to represent ammonia sorption data in these phosphate-containing molecular sieves. At constant coverage, the isosteric heat values have shown the major contribution due to sorbate-sorbent interactions irrespective of the chemical composition.