A new two-dimensional zeolitic imidazolate framework (named as ZIF-L) was synthesized in zinc salt and 2-methylimidazole (Hmim) aqueous solution at room temperature. ZIF-L (Zn(mim)₂·(Hmim)_1/2·(H₂O)_3/2 or C₁₀H₁₆N₅O_3/2Zn) has unique cushion-shaped cavities and leaf-like crystal morphology, and exhibits excellent CO₂ adsorption properties.

A two-dimensional zeolitic imidazolate framework (ZIF), ZIF-L, with a unique anisotropic pore system makes it an excellent material for investigating ZIF membranes with crystallographically preferred orientation and their effects on gas separation properties. A b-oriented ZIF-L membrane was successfully prepared from a randomly oriented seed layer. In contrast, a c-oriented ZIF-L crystal layer was attached to a support through vacuum filtration in the presence of polyethyleneimine. After a short-time secondary growth, the oriented layer grew into a continuous membrane with a high degree of c-out-of-plane orientation. Gas separation studies demonstrated the orientation-dependent separation behavior. In single gas permeation experiments, the c-oriented ZIF-L membrane has higher ideal selectivities of 8.1 for H₂/N₂ and 24.3 for H₂/CO₂ compared to the corresponding values of 3.9 and 5.5 for the b-oriented ZIF-L membrane. The results of binary gas permeation showed decreased separation factors of the c-oriented membrane, but were still much higher than those of the b-oriented membrane. This work provides new insights into controlling ZIF membrane orientation for achieving desirable gas separation performance.

Zeolitic imidazolate frameworks ZIF-8 and ZIF-67 were prepared from stoichiometric metal and ligand aqueous solutions at room temperature within 10 min. Triblock copolymer and ammonium hydroxide are both essential for the formation of ZIFs. Ammonium hydroxide in the aqueous solution deprotonates 2-methylimidazole, and the PEO groups of the triblock copolymer surfactant electrostatically attract metal ions, leading to the formation of ZIF-8 and ZIF-67. The ZIF-8 yield is more than 98%, which is the highest so far. This method is very promising for efficient and environmentally friendly synthesis of ZIFs for practical applications.