NOVELTY - Method-I of forming zeolite FAU(Y) nanocrystals, comprises: (i) combining a solution comprising double deionized water, aqueous tetramethylammonium hydroxide solution (25 wt.%), and an appropriate amount of aluminum isopropoxide; (ii) stirring the solution until it is optically clear; (iii) adding and dissolving an amount of tetramethylammonium bromide in the solution; (iv) adding aqueous colloidal silica to the solution to form a completed solution; (v) sealing the completed solution; (vi) aging and stirring the completed solution; and (vii) heating and stirring the completed solution.    USE - The methods are useful for forming zeolite FAU(Y) nanocrystals, phenethyl functionalized zeolite FAU(Y) nanocrystals, and phenethyl functionalized zeolite BEA nanocrystals (all claimed), which are useful for membrane separation applications like gas separations, and in polymer-exchange-membrane fuel cells.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) method-II of forming phenethyl functionalized zeolite FAU(Y) nanocrystals, comprising (i)-(iv) steps as above per se, adding an appropriate amount of phenethyl trimethoxysilane to form a completed solution, (v) and (vi) steps as above per se, and heating and stirring the completed solution to form the phenethyl functionalized zeolite FAU(Y) nanocrystals; and    (2) method-III of forming phenethyl functionalized zeolite BEA nanocrystals, comprising either combining a solution comprising of double de-ionized water, aqueous tetraethylammonium hydroxide solution (35 wt.%), and an appropriate amount of aluminum isopropoxide, (ii) step as above per se, adding an appropriate amount of aqueous colloidal silica (30 wt.%), adding an appropriate amount of phenethyl trimethoxysilane to foam a completed solution, (v) and (vi) steps as above per se, heating and stirring the completed solution to from the phenethyl functionalized zeolite BEA nanocrystals, or forming an aluminum precursor solution, forming a silica precursor solution, stirring the aluminum precursor solution until it is optically clear, combining the aluminum precursor and the silica precursor solutions to form a combined solution, mixing the combined solution together, sealing the combined solution to form a sealed combined solution, and reacting the sealed combined solution to form the phenethyl functionalized zeolite BEA nanocrystals.