Method of preparing decadodecasil 3R type zeolite membranes and membranes prepared thereby

A method of preparing a DDR (decadodecasil 3R) type zeolite membrane comprising:

• (a) hydrothermally synthesizing DDR type zeolite particles through a seed growth by adding DDR type zeolite particles to a synthetic precursor containing 1-adamantanamine and forming a seed layer by depositing DDR type zeolite particles on a porous substrate;
• and
• (b) preparing a hydrophobic DDR type zeolite membrane through a second seed growth by adding the substrate on which the seed layer is formed to a silica source synthetic precursor that contains a silica source and a methyltropinium salt and performing a hydrothermal synthesis,
• wherein the hydrophobic DDR type zeolite membrane has an out-of-plane orientation in which a specific plane is formed in parallel with the membrane surface and a pore structure perpendicular to the specific plane is aligned in a direction along the membrane thickness.