Rapid One-Pot Microwave Synthesis of Mixed-Linker Hybrid Zeolitic-Imidazolate Framework Membranes for Tunable Gas Separations

Abstract

The relatively slow and complex fabrication processes of polycrystalline metal-organic framework (MOF) membranes often times restrict their way to commercialization, despite their potential for molecular separation applications. Herein, we report a rapid one-pot microwave synthesis of mixed-linker hybrid zeolitic-imidazolate framework (ZIF) membranes consisting of 2-methylimidazolate (ZIF-8 linker) and benzimidazolate (ZIF-7 linker) linkers, termed ZIF-7-8 membranes. The fast-volumetric microwave heating in conjunction with a unique counter diffusion of metal and linker solutions enabled unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes in ∼90 s, the fastest MOF membrane preparation up to date. Furthermore, we were able to tune the molecular sieving properties of the ZIF-7-8 membranes by varying the benzimidazole-to-2-methylimidazole (bIm-to-mIm) linker ratio in the hybrid frameworks. The tuning of their molecular sieving properties led to the systematic change in the permeance and selectivity of various small gases. The unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes with tunable molecular sieving properties is an important step forward for the commercial gas separation applications of ZIF membranes.

Synthesis and functionalisation of spherical meso-, hybrid meso/macro- and macro-porous cellular silica foam materials with regulated pore sizes for CO2 capture

“…Consequently, the development of alternative cost-effective PCC technologies has received tremendous attention over recent years, with the adsorption-based solid adsorbent looping technology having become the persistent focus of many investigations due to the potentially signicantly reduced energy penalty and the choice of a wide range of candidate adsorbent materials, including but not limited to zeolites, 6,7 immobilized amines, 8,9 activated carbons, 10,11 metal-organic frameworks (MOFs), 12,13 covalentorganic frameworks (COFs) 14,15 and zeolitic imidazolate frameworks. 16,17 Among the candidate sorbent materials, immobilized amines possess many desirable CO 2 adsorptive properties that may not be easily obtained with other sorbent materials, such as their extremely high CO 2 selectivity, fast adsorption kinetics and high adsorption capacity especially at very low CO 2 partial pressures, great moisture tolerance and favourable operating temperature window of 50-80 C that minimizes or essentially eliminates the cooling need of typical ue gas streams from power plants. [18][19][20][21][22][23] The CO 2 adsorption of immobilised amine adsorbents follows similar reaction mechanisms to those in the aqueous amine absorption process, which involves the reversible formation of ammonium carbamate under anhydrous ue gas conditions and ammonium bicarbonate under wet conditions.…”

Metal–Organic Framework Membranes: From Fabrication to Gas Separation

“…This approach is built on the dipping of the support in the mother solution of the targeted MOF, and then sealing and heating it to the targeted preset temperature [58][59][60][61]. Instead of conventional oven heating, the microwave irradiation can be used [57,[62][63][64][65][66]. In their first work, Lai and Jeong et al used this method to grow MOF-5 as a thin film on a non-modified porous alumina support, which is considered to be the first reported continuous and well-intergrown membrane in the MOF field ( Figure 3) [56].…”

“…Recently, Jeon et al also used a rapid one-pot solvothermal microwave growth approach to fabricate a mixed-linker ZIF membranes [66]. The mixed-linker ZIF consisted of the ZIF-8 linker the 2-methylimidazolate (mIm) and the ZIF-7 linker the benzimidazolate (bIm), and these were termed as the ZIF-7-8 membranes (Figure 55).…”

“…Binary testing of (a) H2/CH4 and (b) CO2/CH4 for ZIF-7-8 membranes with varying bIm incorporation (adapted with permission from ref. [66]).…”

“…Binary testing of (a) H 2 /CH 4 and (b) CO 2 /CH 4 for ZIF-7-8 membranes with varying bIm incorporation (adapted with permission from ref. [66]). Comparison of (a) H2/CH4 and (b) CO2/CH4 separation performance for mixed-ligand ZIF-7-8 membranes with the parent ZIF membranes (ZIF-7 and ZIF-8).…”