Zeolitic imidazole framework-8 (ZIF-8) with a novel porous hydrangea-like morphology was successfully synthesized with solvothermal synthesis using zinc nitrate as the metal source and 2-methylimidazole as the organic ligand. The effects of reaction temperature and reaction time on the morphology of the crystal were investigated and the samples were characterized in detail. The results show that the porous hydrangea-like ZIF-8 crystal can be obtained at different temperatures from 110 to 140 °C. At the same temperature, with the increase of reaction time, the particles are transformed from porous hydrangea-like into the rhombohedral polyhedron. Combining primary particle self-assembly with Ostwald ripening , we propose a mechanism for the formation of porous hydrangea-like ZIF-8 in a classical crystal growth pathway. In comparison, ZIF-8 with rhombohedral polyhedron can be quickly synthesized via microwave-assisted synthesis.
Metal-organic frameworks (MOFs) have been extensively studied as candidate materials for enzyme immobilization over recent years. In this work, carbonic anhydrase was immobilized in ZIFs by “in situ” immobilization method. The growth state of ZIF-8 was adjusted by adjusting the ratio of Zn 2+ and 2-Hmim to obtain crystals with different morphologies (cubic-, dodecahedral- and leaf-shape). In addition, different surfactants (cationic surface-active agent, an-ionic surfactant, and non-ionic surface-active agent) were added as “shape-inducing agents” to further regulate the crystal shapes, thus affecting the activity of enzyme immobilization in ZIFs. Through CO 2 absorption test, it was found that the thick leaf-shaped CA/ZIF-L-(PVP) induced by PVP had a higher relative activity (150%) than other shapes (cubic, dodecahedral, “burr puzzle” shape, “interpenetration leaves” shape, etc.) of immobilized enzymes. In addition, CA/ZIF-L-(PVP) exhibited excellent reusability and stability, which maintained a relative activity of 131% after 5 cycles, and remained approximately 99% relative activity after 15 days at 40 °C in MDEA solution.
Li Yin,Meiling Li,Hailun Xia,Shanshan Mao,Fangyuan Gai,Hao Wang
The gas separation performance of hybrid carbon molecular sieve membranes is critically influenced by the particle size of the fillers. Herein, ZIF-8 crystals of different sizes (≈50 nm, ≈500 nm, and ≈1 µm) are used as fillers to synthesize a series of ZIF-8-derived-carbon hybrid carbon molecular sieve membranes with high filler loading. As the ZIF-8 crystal size increases from nanoscale to microscale, the CO 2 permeability of the resulting hybrid carbon molecular sieve membrane for a CO 2 /CH 4 binary mixture increases, reaching 9965 Barrer with a selectivity of 28.05. This trend highlights a clear correlation between filler size and gas separation performance of the hybrid carbon molecular sieve membranes. Microscale ZIF-8-derived-carbon offers synergistic advantages by providing abundant hierarchical pores for molecular sieving and continuous, long pathways for efficient gas transport, while preventing particle aggregation under high loading. Our finding provides valuable insights for the further development of high-performance hybrid carbon molecular sieve membranes.
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