ZIF-67 Membranes Synthesized on α-Al₂O₃-Plate-Supported Cobalt Nanosheets with Amine Modification for Enhanced H₂/CO₂ Permselectivity

Abstract

The well-cross-linked ZIF-67 membranes with a thickness of ca. 3 μm were fabricated using α-Al2O3-supported cobalt nanosheets layer (Co-NSL) as an inorganic surface modifier. During the formation of ZIF-67 membranes, Co-NSL served as nucleation centers and cobalt source. Single-gas permeation experiments indicated that the synthesized ZIF-67 membranes showed satisfactory molecular sieving properties, with their H2 permeance reaching 1.48 × 10–6 mol s–1 m–2 Pa–1. The corresponding ideal separation factors of H2 over CO2, N2, and CH4 were 16.8, 16.5, and 18.0, respectively. After treatment with ethylenediamine, the amine-modified ZIF-67 membranes exhibited satisfactory hydrogen permeance with a high ideal separation factor of 30.0 for H2/CO2. Compared with the available metal-organic framework (MOF) membranes in the literature, the use of Co-NSL as an inorganic surface modifier and the postsynthetic amine modification ensured the formation of thin and stable ZIF-67 membranes with grafted −NH2 groups, leading to satisfactory hydrogen permeances with much enhanced H2/CO2 separation factors.

Preparation of ZIF-8 Membranes on Porous ZnO Hollow Fibers by a Facile ZnO-Induced Method

“…1−3 ZIFs (zeolitic imidazolate frameworks), an important category in MOF materials, possess ultra-microporosities, great chemical stability, and thermostability when compared with other MOFs. 4,5 ZIFs have been widely used to adsorb and separate gases and have also been found in the fields of pervaporation, chemocatalysis, and sensors. 6−12 ZIF-8, the classical ZIF compound that has a sodalite zeolite-type structure, is a suggested candidate material for membranebased applications.…”

“…MOFs, that is, metal organic frameworks, exhibit extensive 3D structures and are prepared by linking together the tetrahedral metal ions and the imidazolate linkers. These materials have particular pore sizes, unique chemical properties, and large surface area, which enable them to find utility in the field of separation. − ZIFs (zeolitic imidazolate frameworks), an important category in MOF materials, possess ultra-microporosities, great chemical stability, and thermostability when compared with other MOFs. , ZIFs have been widely used to adsorb and separate gases and have also been found in the fields of pervaporation, chemocatalysis, and sensors. − ZIF-8, the classical ZIF compound that has a sodalite zeolite-type structure, is a suggested candidate material for membrane-based applications. − The in situ growth, secondary seeding growth, and interfacial and vapor-phase processing methods as well as contra-diffusion techniques have so far been explored for MOF membrane synthesis. − MOF membranes without defects are not easy to be prepared by the in situ solvothermal approaches because the MOF heterogeneous nucleation density is low in the supports. Support chemistry exerts an important influence on the synthesis of membranes.…”

Zeolitic Imidazolate Framework Membranes with a High H2 Permeance Fabricated on a Macroporous Support with Novel Spherical Porous Hybrid Materials

“…We found that only petal-like products (cobalt carbonate hydroxide) existed on the surface of the unmodified support. 41 To solve this problem, we deposited more ZIF-8-IPTMS hybrid materials on the support (Figure 5a), aiming to provide an adequate number of heterogeneous nucleation sites. From the SEM image (Figure 5b), we could observe that the as-prepared ZIF-67 membrane was well intergrown and had no obvious defects compared with the membrane prepared with a relatively low deposition amount of ZIF-8-IPTMS hybrid materials (Figure S8).…”

“…This result could also be verified by a control experiment in which a ZIF-67 membrane was synthesized on the surface of an unmodified support (Figure S7). We found that only petal-like products (cobalt carbonate hydroxide) existed on the surface of the unmodified support . To solve this problem, we deposited more ZIF-8-IPTMS hybrid materials on the support (Figure a), aiming to provide an adequate number of heterogeneous nucleation sites.…”

Separation Performance of Si-CHA Zeolite Membrane for a Binary H2/CH4 Mixture and Ternary and Quaternary Mixtures Containing Impurities

“…Comparison of the separation performance of our Si-CHA (symbol red ▲) membrane with polymeric membranes with symbol black ● present (a) in the H 2 /CH 4 separation Robeson plot and (b) separation index plot with other membranes: ZIF-67 , with symbol purple ⬟, ZIF-7-8 with symbol gold ⬟, SAPO-34 with symbol black ★, SSZ-13 with symbol black ▲, ZIF-8 with symbol purple ▶, UIO-66 with symbol pink ◀, SAPO-17 with symbol green ■, and HS with symbol red ▼ membranes and mixed-matrix membranes − with symbol red ■.…”