Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

Luminescent Functional Metal–Organic Frameworks

Synthesis of metal-organic frameworks (MOFs): routes to various MOF topologies, morphologies, and composites.

Metal Organic Frameworks in Biomedicine Patricia Horcajada,* Ruxandra Gref, Tarek Baati, Phoebe K. Allan, Guillaume Maurin, Patrick Couvreur, G erard F erey, Russell E. Morris, and Christian Serre* Institut Lavoisier, UMR CNRS 8180, Universit e de Versailles St-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France Facult e de Pharmacie, UMR CNRS 8612, Universit e Paris-Sud, 92296 Châtenay-Malabry Cedex, France Institut Charles Gerhardt Montpellier, UMR CNRS 5253, Universit e Montpellier 2, 34095 Montpellier cedex 05, France EaStChem School of Chemistry, University of St. Andrews Purdie Building, St Andrews, KY16 9ST U.K.

Metal-organic frameworks in biomedicine.

Postsynthetic methods for the functionalization of metal-organic frameworks.

Fe(III)-carboxylate nanoscale metal−organic frameworks (NMOFs) with the MIL-101 structure were synthesized using a solvothermal technique with microwave heating. The ∼200 nm particles were characterized using a variety of methods, including SEM, PXRD, nitrogen adsorption measurements, TGA, and EDX. By replacing a percentage of the bridging ligand (terephthalic acid) with 2-amino terephthalic acid, amine groups were incorporated into the framework to provide sites for covalent attachment of biologically relevant cargoes while still maintaining the MIL-101 structure. In proof-of-concept experiments, an optical contrast agent (a BODIPY dye) and an ethoxysuccinato-cisplatin anticancer prodrug were successfully incorporated into the Fe(III)-carboxylate NMOFs via postsynthetic modifications of the as-synthesized particles. These cargoes are released upon the degradation of the NMOF frameworks, and the rate of cargo release was controlled by coating the NMOF particles with a silica shell. Potential utility of th...

Postsynthetic Modifications of Iron-Carboxylate Nanoscale Metal−Organic Frameworks for Imaging and Drug Delivery

Computed tomography (CT) is a powerful diagnostic tool based on X-ray attenuation by a specimen, and is capable of providing three-dimensional (3D) images with excellent spatial resolution. A contrast agent with high X-ray attenuation, typically materials containing elements with a high Z number such as iodine, barium, and bismuth, is often used in CT imaging to provide better contrast between the tissue of interest and its surroundings. The only CT contrast agents currently approved for clinical use are iodinated aromatic molecules, and barium sulfate for gastrointestinal tract imaging. CT imaging with small-molecule contrast agents is limited by their nonspecific distribution, rapid renal clearance, and rapid extravasation from blood and lymphatic vessels. Large doses of small-molecule agents (tens of grams) are typically needed to provide adequate contrast, which sometimes cause adverse reactions for the patients. These limitations can be overcome by nanoparticulate contrast agents that can carry a high payload and be functionalized to increase blood circulation times and to endow target specificity. Nanoparticles do not readily diffuse into extravascular space or undergo rapid renal clearance, thus allowing adequate time for accumulation at a disease site. These advantages could allow for a larger time window for imaging and enhanced image contrast at a lower dose. Several nanoparticle systems including Bi2S3, [4] gold, and iodinated organic nanoparticles, have recently been evaluated as next-generation CT contrast agents. However, it is challenging to formulate nanoparticles with high loadings for elements having high Z numbers that are also nontoxic and able to be cleared from the body in a timely fashion. Coordination polymers have recently emerged as interesting functional materials that are readily synthesized by coordination-directed self-assembly of metal ions and organic bridging ligands. Our research group and others have recently demonstrated the synthesis of a new class of nanomaterials by scaling down coordination polymers to the nanoregime. These nanoscale coordination polymers (NCPs) have already shown great potential in biosensing, magnetic resonance imaging, and drug delivery. Given the clinical utility of iodinated aromatic molecules in CT imaging, we surmised that iodinated NCPs could have potential applications as CT contrast agents owing to their ability to carry a very high payload of iodine. Herein we report the synthesis of new iodinated coordination polymers and their scale down to the nano-regime. We also demonstrate the ability of iodinated NCPs to attenuate X-rays in phantom studies. As shown in Scheme 1, five new coordination polymers were synthesized using 2,3,5,6-tetraiodo-1,4-benzenedicarboxylic acid (I4-BDC-H2) bridging ligands and Cu II or Zn

Sylvie Tran

Papers

Postsynthetic Modifications of Iron-Carboxylate Nanoscale Metal−Organic Frameworks for Imaging and Drug Delivery

Iodinated Nanoscale Coordination Polymers as Potential Contrast Agents for Computed Tomography