Design, Properties And Applications Of Novel Magnetic Metal-Organic Framework Nanocomposites

Nanoporous Metal-organic frameworks (MOFs) are a new class of porous crystalline materials with low density and high surface area. Very recently, a new kind of controlled drug delivery system was developed by choosing MOFs. It has been clearly demonstrate that MOFs possess great advantages to achieve high drug loading as well as facile controlled release kinetics, in comparison with conventional drug delivery systems. However, for conventional drug carrier systems, as well as these MOF-based drug carriers, it was difficult to delivery the drug, such as anticancer agents with high concentration, because the drug was diffused by the blood flow before reaching the diseased part.Given porous magnetic core-shell composites offer the provision to the advantages of a porous shell and magnetic responsiveness in many applications, and that MOF-type material possesses many unique properties distinct from other porous materials, it is reasonable to design and construct porous magnetic core-shell structures based on MOFs for potential applications in recyclable catalysts, magnetic separation, targeted drug delivery, and MRI. However, it is still difficult to synthesize MOF-cored materials with inorganic shells, because MOFs are commonly chemically instable in many cases. It is also a great challenge to fabricate core-shell structures with an MOF shell. In this work, we describe a concept for designing and synthesizing a novel kind of magnetic core@MOF shell microspheres with a much more controllable manner and demonstrate the functionlization of these core-shell microspheres. The main contents of this thesis are as follows:1. A novel type of functionalized porous metal-organic framework (MOF) was fabricated by a facile coordination-based postsynthetic modification strategy, and their application for removal of heavy metal ions was demonstrated by Hg2+ adsorption from water. The presence of coordinatively unsaturated Cu(II) centers in [Cu3(BTC)2(H2O)3]n (HKUST-1), provides an accessible way to selectively functionalized HKUST-1 through coordination bonds. The obtained thiol-functionalized [Cu3(BTC)2]n exhibited remarkable adsorption affinity (Kd= 4.73 ×105 mL g-1) and significantly high adsorption capacity (718.14 mg g-1) for Hg2+ adsorption from wastewater. We expect that such thiol-functionalized MOFs will provide an efficient strategy for environmental protection applications to adsorb and remove heavy metal ions from wastewater.2. A novel type of magnetic MOF composite, i.e. Fe3O4/Cu3(BTC)2 nanocomposite, was fabricated at low temperature by conventional electric heating. The results clearly reveal that Fe3O4 nanoparticles were successfully incorporated into nanocrystals of Cu3(BTC)2 (HKUST-1). The material exhibited magnetic characteristics and high porosity for their applications in targeted drug delivery and separation. Up to 0.2 g of nimesulide, a drug for pancreatic cancer treatment, could be adsorbed in the nanocomposite, and it took as long as 11 d to the complete drug release in physiological saline at 37℃. We expect that such a Fe3O4@MOF nanocomposite will provide an efficient platform for targeted drug delivery, magnetic resonance imaging, and magnetic separation, due to their magnetic response and tunable porosity. To the best of our knowledge, this is the first example for the construction of targeted drug delivery system based on MOF materials.3. A novel multifunctional magnetic core@MOF shell microspheres, i.e. Fe3O4@Cu3(BTC)2, with a much more controllable manner were fabricated by a versatile layer-by-layer strategy. The representative SEM and TEM images clearly show that magnetite particles are individually coated with a uniform Cu3(BTC)2 shell, and the shell thickness could be easily tuned by varying layer number coated on the magnetic core. Further, by using a post-synthetic strategy, the MOF shell of the magnetic microsphere was functionalized by thiol groups, and has demonstrated its magnetic separation and a high affinity and high selectivity for Hg2+ and Pb2+ over other competing metal ions in wastewater. These findings may lead to the development of a new type of magnetic Fe3O4@MOF-based nanomaterials for the recovery and removal of heavy metal toxins from human blood and living tissue.4. In the domain of health, one important challenge is the efficient delivery of drugs in the body using non-toxic nanocarriers. Here, an nontoxic porous iron-based MOF magnetic core-shell microspheres, i.e., Fe3O4@MIL-100(Fe), also have been synthesized with a much more controllable manner by a versatile layer-by-layer strategy. The representative SEM and TEM images clearly show that the shell thickness of the magnetic microspheres could be easily tuned from 30 to 400 nm by coating magnetic core with MIL-100(Fe) layers number from 10 to 40. Remarkably, the Fe3O4@MIL-100(Fe) matrix adsorbed 0.65 g of Nimesulide/gram of dehydrated sample by elemental analysis, and it took as long as 22 d to the complete drug release in physiological saline at 37℃. The nontoxic nature and strong magnetic characteristics of Fe3O4@MOF(Fe)-based, coupled with unusually large loading of drug, make them ideal candidates for the field of targeted drug delivery.