Preparation Of Gelatin/Metal Organic Frameworks Composite Membrane And Their Applications

Metal-organic frameworks (MOFs), a new class of porous crystalline materials, are highly desirable for applications including separation, adsorbents, and chemical sensing due to their unique porous structures, pore size tailorability, and tunable sorption behavior. However, difficulties including heterogeneous nucleation on support, high energy consumption, using of expensive organic solvent, and the formation of defects and cracks hind the preparation of MOF membranes. Gelatin, a low cost and abundant fibrous protein with multifunctional groups, has been widely applied in many fields including drug delivery, tissue engineering and separation membranes. In this work, we synthesized gelatin/MOFs composite membrane. Using it, we fabricated the dense and well intergrown ZIF-8/gelatin thin film composite membrane, investigated formation process on PVDF hollow fiber support and their liquid separation performance, and used the composited memranes as precousors to synthesiz hierarchical porous nitrogen-doped carbon film and used as electrode for supercapacitors. The contents of this research are as follows:1. Gelatin/ZIF-8 composite film was prepared using gelatin/zinc hydroxide nanostrands as the precursor. The ZIF-8 seeds were anchored firmly in the gelatin film, which could overcome the poor bonding between the substrate and the MOF layer. This is a simple, effective, economical and environmental method to prepare MOF seeds.2. The dense and well intergrown ZIF-8/gelatin thin film composite membrane was obtained using above seeds. The continuous and well intergrown membranes with a ZIF-8 layer of about 2 μn, exhibited H2 permeance of 7.68 × 10-6 mol s-1Pa-1 m-2at room temperature, with ideal selectivities for H2/CH4 and H2/N2 gases of 14.2 and 9.4, respectively, far beyond the Knudsen selectivity. Similarly, an HKUST-1 seeds/gelatin thin film was also synthesized. This process holds the potential for synthesis of other MOF membranes on various substrates.3. Hollow fiber module bear many merits, such as high packing density and area/volume ratio, which is widely used in the industrial water treatment. Besides, polymer hollow fiber shows low fabrication costs and process feasibility in contrast with inorganic-supported (Al2O3, SiO2) membranes. We synthesized continuous and well intergrown ZIF-8 membrane on surface of PVDF hollow fiber which was applied for liquid separation. The rejection of RhB reaches 98% with permeance of 69 L m-2 h-1 bar-1.4. Free-standing mesoporous nitrogen-doped carbon films were obtained through carbonizing gelatin/HKUST-1 porous composite film. Since gelatin riches in nitrogen element, the porous gelatin/HKUST-1 composite film was a promising precursor for the preparation of the porous nitrogen-doped carbon film. The optimum technological conditions was as follows:carbonization temperature was 900 ℃, the heating rate was 15 ℃/min, the carbonization time was 2h. This mesoporous nitrogen-doped carbon film was explored as an electrode for supercapacitor and exhibited a specific capacity of 316 Fg-1 at a current density of 500 mAg-1, and high capacitance retention of 90% even after charging/discharging for 10000 cycles.