ZIF-67 Membranes Synthesized on α-Al<sub>2</sub>O<sub>3</sub>-Plate-Supported Cobalt Nanosheets with Amine Modification for Enhanced H<sub>2</sub>/CO<sub>2</sub> Permselectivity
Zhongming Zhou, Chao Wu, Baoquan Zhang
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.