Heteroepitaxial growth of vertically orientated zeolitic imidazolate framework‐L (Co/Zn‐ZIF‐L) molecular sieve membranes

Abstract

Despite the extensive potential of zeolitic imidazolate framework (ZIF) membranes in gas separation, the development of continuous, oriented ZIF membranes onto a polymeric substrate remains a significant challenge. This is presumably due to weak adhesion, and insufficient heterogeneous nucleation sites on the polymer surface. Herein, a layer of horizontally aligned poly(sodium‐4‐styrene sulfonate)‐modified halloysite nanotubes (PSS‐HNTs) with ample nucleation sites was used for templated growth of vertically oriented Zn‐ZIF‐L layers. Then we successfully developed the first well‐intergrown membranes of Co‐ZIF‐L on Zn‐ZIF‐L layers via heteroepitaxial growth. The stepwise deposition was utilized for the control of ZIF films orientation to avoid random nucleation and twins overgrowth. The integration of preferred vertical orientation and optimized grain boundary structure endowed the Co/Zn‐ZIF‐L membranes with a remarkable gas separation performance (CO2 permeance: 244.9 GPU, and CO2/N2 selectivity: 17.8). Our methodology provides a useful guideline to design mixed‐component, vertically oriented ZIF‐L to improve gas separation performance.

Facile fabrication of zeolitic imidazolate framework hollow fibre membranesviaa novel scalable continuous fluid circulation process

“…Please do not adjust margins Based on the above results, the CFC-assisted impregnation seeding technique allows for the formation of a more typical seeding morphology similar to those in previous studies. 40,54 In the studies of the sequence of ligand and metal solution circulation, it was found that the formation of seeds can also be controlled by rearranging the order of ligand and metal impregnation, where applying metal impregnation prior to ligand forms larger and more evident seeds on the surface (Fig. S3).…”

Solution-diffusion properties of C4H6 and N2 molecules in zeolitic-imidazolate framework based mixed matrix membranes

“…The low selectivity at high temperature indicates that the temperature should be maintained at 40°C for further membranes testing. From the previously reported works [26,39], it was concluded that the separation of the hydrocarbons through the gas separation system was affected by the high temperature, so that the low operating temperature favored the recovery of hydrocarbons from the mixed nitrogen stream. Consequently, 40°C temperature was selected for further testing of these membranes.…”

“…It is worth noticing that; besides the extensively researched linker-substituted effect, metal-substitution also influences the molecular sieving efficiency of the associated ZIF crystals. By introducing a second metal ion in the MOF cluster, the stability and affinity towards the target gases can be largely improved [39][40][41] . Many recent works have reported in which researchers have used mixed metal MOFs by adding another metal in the ZIF-8 crystal for properties enhancement 41 .…”

Vapor linker exchange of partially amorphous metal–organic framework membranes for ultra‐selective gas separation

“…Membrane technology can efficiently separate raw reagents and products of chemical, pharmaceutical, environmental, and energy-related industries. 1,2 Benefiting from the uniform and regular nanoporous structures, polycrystalline membranes, comprising of zeolites, [3][4][5][6] metalorganic frameworks (MOFs), [7][8][9][10][11][12][13][14][15] covalent-organic frameworks, 16 and so on, show outstanding performance for precisely molecular separations.…”

“…Membrane technology can efficiently separate raw reagents and products of chemical, pharmaceutical, environmental, and energy‐related industries 1,2 . Benefiting from the uniform and regular nanoporous structures, polycrystalline membranes, comprising of zeolites, 3–6 metal–organic frameworks (MOFs), 7–15 covalent‐organic frameworks, 16 and so on, show outstanding performance for precisely molecular separations. But for the binary or multiple mixtures with small and similar molecular diameters, for example of H 2 and CO 2 with difference in kinetic diameters (KD) of only 0.4 Å, their separation through these membranes is still a tough challenge, 17 because the controlling of transport nanochannels in subatomic levels is difficult and the lattice flexibility of polycrystalline membranes causes pore variation 18,19 .…”