(395e) Phase Inversion Synthesis of ZIF-8/Polymer Spheres for Gas Adsorption

Carbon dioxide separation is a key step in carbon sequestration for preventing global warming with the increasing of the energy consumption. Adsorption is one of the most important methods to separate compounds from industrial gas mixtures. Thus, there is growing interest in developing technologies for the efficient adsorption of large quantities of carbon dioxide. The adsorbent materials are restricted to porous materials with a high surface/volume ratio. Metal organic frameworks (MOFs) are a new class of porous crystalline materials consisting of metal ions linked by organic bridging ligands. Zeolitic imidazolate frameworks (ZIFs), a subfamily of MOFs, have exceptional thermal and chemical stability; in particular, ZIF-8 is one of the most studied materials because of its functional applications in gas separation. However, one of the big issues to use ZIF-8 particles as adsorbent is how to shape them to a particular form. In the industrial gas separation processes, columns packed with adsorbents are mainly utilized, and the most common forms of adsorbents are the beads and the granules.

Here, we report a phase inversion spinning method for the preparation of the macroporous spheres through a single orifice spinneret. In principle, this method is a one-step method to synthesize ZIF-8 spheres with polymer as the binder, and the diameter of the spheres is controllable by changing the size of the spinneret. In a typical phase inversion process, the spheres are produced by extruding a concentrated polysulfone solution containing different amount of ZIF-8 through a single orifice spinneret. Surfactant F127 is pre-added in the polysulfone solution as a pore-forming agent. The morphology of the sphere shows a porous structure of the sphere with a pore diameter of around 1 µm, and the porosity of sphere is around 77% by the influence of the F127. The resulting ZIF-8/polymer composite spheres were analysed by nitrogen adsorption analysis, single carbon dioxide adsorption at different temperatures, and single hydrogen adsorption. The spheres containing 80% of ZIF-8 shows a high BET surface area which is appropriate 760 m²/g, indicated the spheres are almost fully covered with ZIF-8 particles. The gas adsorption analysis of the ZIF-8/polymer spheres with nitrogen, carbon dioxide, and hydrogen show impressive value compared with the ZIF-8 powder; in addition, the spheres have the advantages of easy handling and recycling over ZIF-8 powder. This phase inversion method is a one-step method to synthesize spheres, which has potential to use for other adsorbent materials shaping.