Layered ZIFs Using a Surfactant as a Structure Directing Agent

Zeolitic imidazolate frameworks (ZIFs) are three-dimensional (3D) porous materials with only a few exceptions - ZIF-L, Zn₂(benzimidazole)₄, etc. Herein, we report the synthesis of a new layered ZIF, which we call ZIF-S. We use a surfactant (sodium dodecyl sulfate) as a structure-directing agent, analogous to the concept used in the synthesis of zeolites. The layers contain individual ZIF sheets intercalated by surfactants. Its ordered structure belongs to the tetragonal lattice with the <i>P</i>4̅2₁<i>m</i> space group. The unit cell parameters are <i>a</i> = <i>b</i> = 16.82 Å; <i>c</i> = 24.5 Å at room temperature. The layered material undergoes topotactic condensation and forms its parent material (ZIF-8 or ZIF-67, depending on the metal node) upon heating to or above 200 °C. ZIF-S layers could be obtained with a large lateral size and a high aspect ratio, which is ideal for the scalable preparation of gas-selective membranes, thanks to the presence of pore apertures suitable for the separation of small gas molecules. Fabrication of gas-selective membranes from a simple coating of ZIF-S is demonstrated.