Abstract:
The disclosure relates generally to materials that comprise organic frameworks. The disclosure also relates to materials that are useful to store and separate biological agents that are environmentally friendly and biocompatible.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 60/975,089, filed Sep. 25, 2007, the disclosures of which is incorporated herein by reference. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The disclosure relates generally to materials that comprised metal organic frameworks. The disclosure also relates to materials that are useful to deliver molecules in a biological system as well as biological sensors. 
       BACKGROUND 
       [0003]    Existing metal organic frameworks are toxic and lack biocompatibility. 
       SUMMARY 
       [0004]    The disclosure provides porous biocompatible metal organic frameworks (bMOFs) developed from non-toxic starting materials. Such bMOF materials can be utilized in drug storage and delivery, flavoring and drying agents in food, catalysis, tissue engineering, dietary supplements, separation technology and gas storage. 
         [0005]    The disclosure provides routes for the design and synthesis of 1, 2 and 3D-biologically useful bMOFs. The 3D-bMOFs of the disclosure are porous and capable of storing, within the pores of the framework, drugs; absorbing biomolecules; being used as a framework for tissue engineering and scaffolds; expansion within the gastrointestinal tract to serve as a dietary supplement; and the like. 
         [0006]    The materials described in the disclosure can be tailored as 2D- or 3D-networks depending upon the metal ions, organic linkers and reaction conditions. With selection of the organic linkers, which represents an integral part of the framework, and reaction conditions such as temperature, pH, solvent systems, reactant ratio and reaction time, the desired framework can be achieved. 
         [0007]    The disclosure provides a biocompatible metal-organic framework (bMOF) comprising: a plurality of biocompatible metallic cores, each core linked to at least one other core; a plurality of biocompatible linking ligands that connects adjacent cores, and a plurality of pores, wherein the plurality of linked cores defines the pore. In one aspect, the plurality of cores are different. In one aspect. At least two of the cores are different. In another aspect, the plurality of linking ligands are different. In yet another aspect, the porous framework is functionalized to bind an analyte or guest species. In yet another embodiment, the pores may be heterogeneous or homogenous in size. 
         [0008]    The disclosure also provides a biocompatible/environmentally friendly metal-organic framework comprising: a plurality of metal clusters, each metal cluster comprising one or more metal ions; and a plurality of non toxic charged multidentate linking ligands that connect adjacent metal clusters. In one embodiment, the linking ligand comprises an alkyl or cycloalkyl group, consisting of 1 to 20 carbon atoms, an aryl group, consisting of 1 to 5 phenyl rings, or an alkyl or aryl amine, consisting of alkyl or cycloalkyl groups having from 1 to 20 carbon atoms or aryl groups consisting of 1 to 5 phenyl rings, and in which multidentate functional groups are covalently bound to the substructure of the ligand. Multidentate functionality can be obtained using a member selected from the group consisting of CO 2 H, CS 2 H, NO 2 , SO 3 H, Si(OH) 3 , Ge(OH) 3 , Sn(OH) 3 , Si(SH) 4 , Ge(SH) 4 , Sn(SH) 4 , PO 3 H, AsO 3 H, AsO 4 H, P(SH) 3 , As(SH) 3 , CH(RSH) 2 , C(RSH) 3 , CH(RNH 2 ) 2 , C(RNH 2 ) 3 , CH(ROH) 2 , C(ROH) 3 , CH(RCN) 2 , C(RCN) 2 , wherein R is an alkyl group having from 1 to 5 carbon atoms, or an aryl group consisting of 1 to 2 phenyl rings; and, CH(SH) 2 , C(SH) 3 , CH(NH 2 ) 2 , C(NH 2 ) 3 , CH(OH) 2 , C(OH) 3 , CH(CN) 2 , and C(CN) 3 . In one embodiment, the linking moiety/ligand comprise carboxylic acid functional groups. This disclosure further includes cycloalkyl or aryl substructure that comprise from 1 to 5 rings that include either all carbon or a mixture of carbon, with nitrogen, oxygen, sulfur, boron, phosphorous, silicon and aluminum atoms making up the ring. 
         [0009]    In one aspect, each ligand of the plurality of multidentate linking ligands includes two or more carboxylates. In another aspect, the metal ions are selected from the group consisting of Li + , Na + , Rb + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Ti 4+ , Zr 4+ , Ta 3+ , Cr 3+ , Mo 3+ , W 3+ , Mn 3+ , Fe 3+ , Fe 2+ , Ru 3+ , Ru 2+ , Os 3+ , Os 2+ , Co 3+ , Co 2+ , Ni + , Pd 2+ , Pd + , Pt 2+ , Pt + , Cu 2+ , Cu + , Au + , Zn 2+ , Al 3+ , Ga 3+ , In 3+ , Si 4+ , Si 2+ , Ge 4+ , Ge 2+ , Sn 4+ , Sn 2+ , Bi 5+ , Bi 3+ , and combinations thereof. In yet a further aspect, the multidentate linking ligand has 6 or more atoms (e.g., twelve or more atoms) that are incorporated in aromatic rings or non-aromatic rings. The one or more multidentate linking ligands can comprise anions of parent compounds selected from the group consisting of citric acid, malic acid, tartaric acid, retinoic acid, pantothenic acid, folic acid, nicitinic acid, oxalic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, alpha-linoleic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, and docosahexaenoic acid. 
         [0010]    The disclosure provides a framework comprising a plurality of metal clusters comprising a metal ion and a linking ligand having a general structure selected from the group consisting of: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal and R is selected from the group consisting of —H, —OH, —OR1, aryl, substituted aryl, alkyl, substituted alkyl, carboxyl, aminocarbonyl, alkylsulfonylaminocarboxyl, alkoxycarbonyl, and halo, wherein R1 can be —H, and aryl, substituted aryl, alkyl, substituted alkyl, carboxyl, aminocarbonyl, alkylsulfonylaminocarboxyl, alkoxycarbonyl, and halo. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal and wherein n is 0, 1, or 2. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; and 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal. 
         [0011]    The bMOFs of the disclosure can further comprise a guest species; the guest species can increase the surface area of the MOF. In one aspect, the guest species is a biological agent (e.g., a protein, polypeptide, peptide, lipid, nucleic acid or small molecule agent). In one aspect, the biological agent is a therapeutic agent or a diagnostic agent. 
         [0012]    The disclosure also provides a dietary supplement comprising a bMOF of the disclosure. Such bMOFs are biocompatible and can be used for delivery of a drug or other biological agent or adsorption of a biological agent within the gastrointestinal tract. In another embodiment, the bMOF may be rendered expandable by absorption of a guest species within the gastrointestinal tract or made such that the framework is biodegradable during a desired time period there by, for example, giving the stimulus of being satiated. 
         [0013]    The disclosure provides a drug delivery composition comprising a bMOF having within its pores a drug, wherein the drug is delivered to the intestinal tract (e.g., an enteric coating). 
         [0014]    In yet another aspect, a food additive comprising a bMOF of the disclosure is provided. 
         [0015]    The disclosure also provides a gas storage device comprising a MOF of the disclosure. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  shows characterization of a MOF of the disclosure. 
           [0017]      FIG. 2  shows characterization of a MOF of the disclosure. 
           [0018]      FIG. 3A-B  shows a bMOF structure (MgBDC1) of the disclosure. (A) Binuclear cluster in MgBDC-1 including Magnesium; Oxygen; and Carbon atoms. (B) 3D view of MgBDC-1. 
           [0019]      FIG. 4A-B  shows a bMOF structure (MgDHBDC-1) of the disclosure (A) Hexanuclear cluster in MgDHBDC-1 including Magnesium; Oxygen; and Carbon atoms. (B) 3D view of MgDHBDC-1. 
           [0020]      FIG. 5  shows an MgOBA-1 structure of the disclosure including Magnesium; Oxygen; and Carbon atoms. 
           [0021]      FIG. 6A-B  shows a bMOF structure of the disclosure (MgBTC-1). (A) shows a binuclear cluster of MgBTC-1 including Magnesium; Oxygen; and Carbon. (B) shows Trigonal links are represented as dark triangles, while light gray triangles represent inorganic SBUs. Empty spaces are illustrated as spheres. 
           [0022]      FIG. 7  shows a bMOF (MgBTB-1) framework of the disclosure. An Octahedral Inorganic SBUs and tritopic links form 2D layer structure. 
           [0023]      FIG. 8A-B  shows a bMOF structure of the disclosure (MgBTB-2). (A) Fundamental building units of MgBTB-2 including Magnesium; Oxygen; Carbon; and Nitrogen. (B) Trigonal links are represented as triangles, while cubes represent inorganic SBUs. Empty spaces are illustrated as spheres. 
           [0024]      FIG. 9A-B  shows a bMOF of the disclosure (MgBTB-3). (A) Fundamental building units of MgBTB-3 including Magnesium; Oxygen; Carbon; and Nitrogen. (B) Inorganic SBUs are represented as squares. Empty spaces are illustrated as spheres. 
           [0025]      FIG. 10  shows a bMOF of the disclosure (MgBTB-4). The structure consists of two types of inorganic SBUs (light and dark triangles and octahedra) and trigonal links. Empty spaces are illustrated as spheres. 
           [0026]      FIG. 11A-B  shows yet another bMOF of the disclosure (MgBBC-1). Trinuclear cluster of MgBBC-1 including Magnesium; Oxygen; and Carbon. (B) shows a space fill model of the 2D structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    As used herein and in the appended claims, the singular forms “a,” “and,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a framework” includes a plurality of such frameworks and reference to “the composition” includes reference to one or more compositions, and so forth. 
         [0028]    Also, the use of “or” means “and/or” unless stated otherwise. Similarly, “comprise,” “comprises,” “comprising” “include,” “includes,” and “including” are interchangeable and not intended to be limiting. 
         [0029]    It is to be further understood that where descriptions of various embodiments use the term “comprising,” those skilled in the art would understand that in some specific instances, an embodiment can be alternatively described using language “consisting essentially of” or “consisting of.” 
         [0030]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices and materials are described herein. 
         [0031]    Any publications discussed above and throughout the text are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior disclosure. 
         [0032]    The use of MOFs comprising using non-toxic components as a drug storage and delivery material has not been reported nor the synthesis of biologically non-toxic MOFs. An advantage of the MOFs of the disclosure compared to previous MOFs is the non-toxic nature of the composition. In addition, the MOFs are highly stable with or without the presence of a guest molecule within the pores of the framework. 
         [0033]    As used herein, a “cluster” refers to a repeating unit or units found in a framework. Such a framework can comprise a homogenous repeating cluster or a heterogeneous repeating cluster structure. A cluster comprises a transition metal and a linking moiety (sometimes referred to as a linking ligand). A plurality of clusters linked together defines a framework. 
         [0034]    A “linking moiety” refers to a mono-dentate, bidentate or multidentate compound that bind a biocompatible metal or a plurality of biocompatible metals, respectively. 
         [0035]    As used herein “linking ligand” or “linking moiety” refers to a chemical species (including neutral molecules and ions) that coordinate two or more metals and the definition of void regions or channels in the framework that is produced. The linking ligand of the disclosure is a non-toxic molecule. Examples of a linking ligand useful in the methods and compositions of the disclosure include citric acid, malic acid, and tartaric acid. Other linking moieties or ligands include, for example, methanoic acid, ethanoic acid, propanoic acid, butanoic acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, mylistic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, succinic anhydride, maleic anhydride, phthalic anhydride, glycolic acid, lactic acid, hydroxybutyric acid, mandelic acid, glyceric acid, malic acid, tartaric acid, citric acid, and ascorbic acid. 
         [0036]    A linking moiety/ligand can comprise an alkyl or cycloalkyl group, consisting of 1 to 20 carbon atoms, an aryl group, consisting of 1 to 5 phenyl rings, or an alkyl or aryl amine, consisting of alkyl or cycloalkyl groups having from 1 to 20 carbon atoms or aryl groups consisting of 1 to 5 phenyl rings, and in which multidentate functional groups are covalently bound to the substructure of the ligand. Multidentate functionality can be selected from the group consisting of CO 2 H, CS 2 H, NO 2 , SO 3 H, Si(OH) 3 , Ge(OH) 3 , Sn(OH) 3 , Si(SH) 4 , Ge(SH) 4 , Sn(SH) 4 , PO 3 H, AsO 3 H, AsO 4 H, P(SH) 3 , As(SH) 3 , CH(RSH) 2 , C(RSH) 3 , CH(RNH 2 ) 2 , C(RNH 2 ) 3 , CH(ROH) 2 , C(ROH) 3 , CH(RCN) 2 , C(RCN) 3 , wherein R is an alkyl group having from 1 to 5 carbon atoms, or an aryl group consisting of 1 to 2 phenyl rings; and, CH(SH) 2 , C(SH) 3 , CH(NH 2 ) 2 , C(NH 2 ) 3 , CH(OH) 2 , C(OH) 3 , CH(CN) 2 , and C(CN) 3 . In one embodiment, the linking moiety/ligand comprise carboxylic acid functional groups. This disclosure further includes cycloalkyl or aryl substructure that comprise from 1 to 5 rings that include either all carbon or a mixture of carbon, with nitrogen, oxygen, sulfur, boron, phosphorous, silicon and aluminum atoms making up the ring. 
         [0037]    Another aspect of this disclosure provides that crystalline metal-organic microporous materials can be synthesized by the addition of a solution of a metal salt to a solution containing an appropriate blend of ligands, some of which contain multidentate functional groups, as described herein, and others of which contain monodentate functional groups, in the presence of a suitable templating agent. 
         [0038]    In one aspect, the linking ligand comprises one or more carboxylates. For example, the linking ligand may be a polycarboxylic acid. As used herein, the term “polycarboxylic acid” indicates a dicarboxylic, tricarboxylic, tetracarboxylic, pentacarboxylic, and like monomeric polycarboxylic acids, and anhydrides, and combinations thereof, as well as polymeric polycarboxylic acids, anhydrides, copolymers, and combinations thereof. 
         [0039]    Illustratively, a monomeric polycarboxylic acid may be a dicarboxylic acid, including, but not limited to, unsaturated aliphatic dicarboxylic acids, saturated aliphatic dicarboxylic acids, aromatic dicarboxylic acids, unsaturated cyclic dicarboxylic acids, saturated cyclic dicarboxylic acids, hydroxy-substituted derivatives thereof, and the like. Or, illustratively, the polycarboxylic acid(s) itself may be a tricarboxylic acid, including, but not limited to, unsaturated aliphatic tricarboxylic acids, saturated aliphatic tricarboxylic acids, aromatic tricarboxylic acids, unsaturated cyclic tricarboxylic acids, saturated cyclic tricarboxylic acids, hydroxy-substituted derivatives thereof, and the like. It is appreciated that any such polycarboxylic acids may be optionally substituted, such as with hydroxy, halo, alkyl, alkoxy, and the like. In one variation, the polycarboxylic acid is the saturated aliphatic tricarboxylic acid, citric acid. Other suitable polycarboxylic acids are contemplated to include, but are not limited to, aconitic acid, adipic acid, azelaic acid, butane tetracarboxylic acid dihydride, butane tricarboxylic acid, chlorendic acid, citraconic acid, dicyclopentadiene-maleic acid adducts, diethylenetriamine pentaacetic acid, adducts of dipentene and maleic acid, ethylenediamine tetraacetic acid (EDTA), fully maleated rosin, maleated tall-oil fatty acids, fumaric acid, glutaric acid, isophthalic acid, itaconic acid, maleated rosin oxidized with potassium peroxide to alcohol then carboxylic acid, maleic acid, malic acid, mesaconic acid, biphenol A or bisphenol F reacted to introduce 3-4 carboxyl groups, oxalic acid, phthalic acid, sebacic acid, succinic acid, tartaric acid, terephthalic acid, tetrabromophthalic acid, tetrachlorophthalic acid, tetrahydrophthalic acid, trimellitic acid, trimesic acid, and the like, and anhydrides, and combinations thereof. 
         [0040]    The disclosure provides a cluster comprising a metal ion and a linking ligand having a general structure selected from the group consisting of: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal and R is selected from the group consisting of —H, —OH, —OR1, aryl, substituted aryl, alkyl, substituted alkyl, carboxyl, aminocarbonyl, alkylsulfonylaminocarboxyl, alkoxycarbonyl, and halo, wherein R1 can be —H, and aryl, substituted aryl, alkyl, substituted alkyl, carboxyl, aminocarbonyl, alkylsulfonylaminocarboxyl, alkoxycarbonyl, and halo. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal and wherein n is 0, 1, or 2. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal; and 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a non-toxic metal. 
         [0041]    General formulas I-VIII above, depict a cluster comprising a metal ion and a linking moiety, however it will be recognized that the linking moieties can be modified or derivatized. For example, the linking moiety as set forth in Formula II can be modified as follows: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein each of R1-15 are independently selected from the group consisting of —H, —OH, —OR 16 , aryl, substituted aryl, alkyl, substituted alkyl, carboxyl, aminocarbonyl, alkylsulfonylaminocarboxyl, alkoxycarbonyl, and halo, wherein R 16  can be —H, and aryl, substituted aryl, alkyl, substituted alkyl, carboxyl, aminocarbonyl, alkylsulfonylaminocarboxyl, alkoxycarbonyl, and halo. 
         [0042]    The term “alkyl” refers to a saturated monovalent chain of carbon atoms, which may be optionally branched; the term “cycloalkyl” refers to a monovalent chain of carbon atoms, a portion of which forms a ring; the term “alkenyl” refers to an unsaturated monovalent chain of carbon atoms including at least one double bond, which may be optionally branched; the term “cycloalkenyl” refers to an unsaturated monovalent chain of carbon atoms, a portion of which forms a ring; the term “heterocyclyl” refers to a monovalent chain of carbon and heteroatoms, wherein the heteroatoms are selected from nitrogen, oxygen, and sulfur, a portion of which, including at least one heteroatom, form a ring; the term “aryl” refers to an aromatic mono or polycyclic ring of carbon atoms, such as phenyl, naphthyl, and the like; and the term “heteroaryl” refers to an aromatic mono or polycyclic ring of carbon atoms and at least one heteroatom selected from nitrogen, oxygen, and sulfur, such as pyridinyl, pyrimidinyl, indolyl, benzoxazolyl, and the like. It is to be understood that each of alkyl, cycloalkyl, alkenyl, cycloalkenyl, and heterocyclyl may be optionally substituted with independently selected groups such as alkyl, haloalkyl, hydroxyalkyl, aminoalkyl, carboxylic acid and derivatives thereof, including esters, amides, and nitriles, hydroxy, alkoxy, acyloxy, amino, alkyl and dialkylamino, acylamino, thio, and the like, and combinations thereof. It is further to be understood that each of aryl and heteroaryl may be optionally substituted with one or more independently selected substituents, such as halo, hydroxy, amino, alkyl or dialkylamino, alkoxy, alkylsulfonyl, cyano, nitro, and the like. 
         [0043]    The disclosure also provides a biocompatible metal-organic framework (bMOF) comprising a homogenous or heterogeneous plurality of clusters, wherein the clusters form a framework. 
         [0044]    A “framework,” as used herein, refers to a framework of repeating clusters having a 2-D or 3-D structure. 
         [0045]    A non-toxic chemical species refers to a chemical that when contacted with a biological organism does not have, or has limited, direct effect on cell apoptosis or death. Such materials can also be referred to as biologically safe, biologically inert, and biocompatible. 
         [0046]    As used herein “non-linking ligand” means a chemical species that is coordinated to a metal but does not act as a linker. 
         [0047]    As used herein “guest” means any chemical species that resides within the void regions of an open framework solid that is not considered integral to the framework. Examples include: molecules of the solvent that fill the void regions during the synthetic process, other molecules that are exchanged for the solvent such as during immersion (via diffusion) or after evacuation of the solvent molecules, such as gases in a sorption experiment. A guest species may be a drug, therapeutic agent or diagnostic agent to be “carried” by the framework of the disclosure. A chemical species is used herein to include peptides, polypeptides, nucleic acid molecules, and fatty acids. Typically a drug will comprise a small organic molecule capable of filling or partially filling a void of a framework. 
         [0048]    In yet another embodiment, the framework can be used as a scaffold for tissue engineering, wherein the framework may be infiltrate by cells or extracellular matrix material (e.g., collagen, elastin and the like) such that it support cell growth. Because the framework is biocompatible cells can grow and proliferate on the framework. 
         [0049]    As used herein “charge-balancing species” means a charged guest species that balances the charge of the framework. Quite often this species is strongly bound to the framework, i.e. via hydrogen bonds. It may decompose upon evacuation to leave a smaller charged species, or be exchanged for an equivalently charged species, but typically it cannot be removed from the pore of a metal-organic framework without collapse. 
         [0050]    As used herein “space-filling agent” means a guest species that fills the void regions of an open framework during synthesis. Materials that exhibit permanent porosity remain intact after removal of the space-filling agent via heating and/or evacuation. Examples include: solvent molecules or molecular charge-balancing species. The latter may decompose upon heating, such that their gaseous products are easily evacuated and a smaller charge-balancing species remain in the pore (i.e. protons). Sometimes space filling agents are referred to as templating agents. 
         [0051]    As used herein “accessible metal site” means a site in a metal cluster and, in particular, a position adjacent to a metal in a metal cluster available for a chemical moiety such as a ligand to attach. 
         [0052]    As used herein “open metal site” means a site in a metal cluster and, in particular, a position adjacent to a metal in a metal cluster from which a ligand or other chemical moiety has been removed, rendering that metal cluster reactive for adsorption of a chemical species having available electron density for attachment to the metal cluster and, in particular, a metal in the metal cluster. 
         [0053]    As used herein “metal cluster” means any metal containing moiety present in a bMOF of the disclosure. This definition embracing single metal atoms or metal ions to groups of metals or metal ions that optionally include ligands or covalently bonded groups. 
         [0054]    In one embodiment of the disclosure, a vehicle for delivery of a biological agent to an organism comprising a bMOF is provided. The bMOF of the embodiment includes a plurality of metal clusters and a plurality of charged multidentate non-toxic linking ligands that connect adjacent metal clusters. Each metal cluster includes one or more metal ions and at least one open metal site. Advantageously, the bMOF includes one or more sites for capturing/binding molecule to be delivered to an organism (e.g., a mammal, including a human). In this embodiment, the one or more sites include the at least one open metal site. Biological agents that may be captured/stored in the frameworks of the disclosure include any biological molecules capable of fitting within a pore and comprising available electron density for attachment to the one or more sites. Such electron density includes molecules having multiple bonds between two atoms contained therein or molecules having a lone pair of electrons. 
         [0055]    In a variation of this embodiment, the open metal site is formed by activating a precursor metal-organic framework. In a refinement, this activation involves removing one or more chemical moieties from the metal cluster. Typically, such moieties are ligands complexed to or bonded to a metal or metal ion within the metal clusters. Moreover, such moieties include species such as water, solvent molecules contained within the metal clusters, and other chemical moieties having electron density available for attachment to the metal cluster and/or metal atoms or ions contained therein. Such electron density includes molecules having multiple bonds between two atoms contained therein or molecules having a lone pair of electrons. 
         [0056]    In another embodiment of the disclosure, a biocompatible metal organic framework is provided, the biocompatible metal organic framework comprises a plurality of metal cores and a plurality of charged non-toxic multidentate linking ligands that connect adjacent metal clusters. Each metal core includes one or more metal ions and at least one accessible metal site. The metal ions are typically alkali earth metals and the ligands are biocompatible acids. Advantageously, the metal-organic framework includes one or more sites for binding or storing a biological molecule or gas. In this embodiment, the one or more sites include the at least one accessible metal site. Gases that may be stored in the gas storage material of the disclosure include gas molecules comprising available electron density for attachment to the one or more sites for storing gas. Suitable examples of such gases include, but are not limited to, the gases comprising a component selected from the group consisting of ammonia, argon, carbon dioxide, carbon monoxide, hydrogen, and combinations thereof. In one variation of this embodiment, the accessible metal site is an open metal site. 
         [0057]    The metal-organic frameworks used in the embodiments of the disclosure include a plurality of pores for adsorption of a biological molecule or gas. In one variation, the plurality of pores has a unimodal size distribution. In another variation, the plurality of pores have a multimodal (e.g., bimodal) size distribution. 
         [0058]    In another variation of the embodiments of the materials set forth above, the metal organic frameworks include metal clusters comprising one or more metal ions. In another variation, the metal-organic frameworks include metal clusters that comprise two or more metal ions. In still another variation, the metal-organic frameworks include metal cores that comprise three or more metal ions. The metal ions can be selected from the group consisting of Li + , Na + , Rb + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Ti 4+ , Zr 4+ , Ta 3+ , Cr 3+ , Mo 3+ , W 3+ , Mn 3+ , Fe 3+ , Fe 2+ , Ru 3+ , Ru 2+ , Os 3+ , Os 2+ , Co 3+ , Co 2+ , Ni 2+ , Ni + , Pd 2+ , Pd + , Pt 2+ , Pt + , Cu 2+ , Cu + , Au + , Zn 2+ , Al 3+ , Ga 3+ , In 3+ , Si 4+ , Si 2+ , Ge 4+ , Ge 2+ , Sn 4+ , Sn 2+ , Bi 5+ , Bi 3+ , and combinations thereof. 
         [0059]    An environmentally friendly metal-organic framework of the disclosure comprises a plurality of metal cores, each metal core comprising one or more metal ions; and a plurality of non toxic charged multidentate linking ligands that connect adjacent metal cores. In one aspect, the each ligand of the plurality of multidentate linking ligands includes two or more carboxylates. In yet another aspect, the multidentate linking ligand has twelve or more atoms that are incorporated in aromatic rings or non-aromatic rings. In a further aspect, the one or more multidentate linking ligands comprise anions of parent compounds selected from the group consisting of citric acid, malic acid, tartaric acid, retinoic acid, pantothenic acid, folic acid, nicitinic acid, oxalic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, alpha-linoleic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, and docosahexaenoic acid. 
         [0060]    The metal-organic framework used in the disclosure optionally further comprises a non-linking ligand. In a variation, the non-linking ligand is selected from the group consisting of O 2− , sulfate, nitrate, nitrite, sulfite, bisulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, diphosphate, triphosphate, phosphite, chloride, chlorate, bromide, bromate, iodide, iodate, carbonate, bicarbonate, sulfide, hydrogen sulphate, selenide, selenate, hydrogen selenate, telluride, tellurate, hydrogen tellurate, nitride, phosphide, arsenide, arsenate, hydrogen arsenate, dihydrogen arsenate, antimonide, antimonate, hydrogen antimonate, dihydrogen antimonate, fluoride, boride, borate, hydrogen borate, perchlorate, chlorite, hypochlorite, perbromate, bromite, hypobromite, periodate, iodite, hypoiodite; and combinations thereof. 
         [0061]    The metal-organic frameworks of the disclosure optionally further comprise space-filling agents, adsorbed chemical species, guest species, and combinations thereof. In some variations of the disclosure, space-filling agents, adsorbed chemical species and guest species increase the surface area of the metal-organic framework. Suitable space-filling agents include, for example, a component selected from the group consisting of: 
         [0062]    (i) alkyl amines and their corresponding alkyl ammonium salts, containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms; 
         [0063]    (ii) aryl amines and their corresponding aryl ammonium salts having from 1 to 5 phenyl rings; 
         [0064]    (iii) alkyl phosphonium salts, containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms; 
         [0065]    (iv) aryl phosphonium salts, having from 1 to 5 phenyl rings; 
         [0066]    (v) alkyl organic acids and their corresponding salts, containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms; 
         [0067]    (vi) aryl organic acids and their corresponding salts, having from 1 to 5 phenyl rings; 
         [0068]    (vii) aliphatic alcohols, containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms; 
         [0069]    (viii) aryl alcohols having from 1 to 5 phenyl rings; 
         [0070]    (a) inorganic anions from the group consisting of sulfate, nitrate, nitrite, sulfite, bisulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, diphosphate, triphosphate, phosphite, chloride, chlorate, bromide, bromate, iodide, iodate, carbonate, bicarbonate, O.sup.2−, diphosphate, sulfide, hydrogen sulphate, selenide, selenate, hydrogen selenate, telluride, tellurate, hydrogen tellurate, nitride, phosphide, arsenide, arsenate, hydrogen arsenate, dihydrogen arsenate, antimonide, antimonate, hydrogen antimonate, dihydrogen antimonate, fluoride, boride, borate, hydrogen borate, perchlorate, chlorite, hypochlorite, perbromate, bromite, hypobromite, periodate, iodite, hypoiodite, and the corresponding acids and salts of said inorganic anions; 
         [0071]    (b) ammonia, carbon dioxide, methane, oxygen, argon, nitrogen, ethylene, hexane, benzene, toluene, xylene, chlorobenzene, nitrobenzene, naphthalene, thiophene, pyridine, acetone, 1,2-dichloroethane, methylenechloride, tetrahydrofuran, ethanolamine, triethylamine, trifluoromethylsulfonic acid, N,N-dimethyl formamide, N,N-diethyl formamide, dimethylsulfoxide, chloroform, bromoform, dibromomethane, iodoform, diiodomethane, halogenated organic solvents, N,N-dimethylacetamide, N,N-diethylacetamide, 1-methyl-2-pyrrolidinone, amide solvents, methylpyridine, dimethylpyridine, diethylethe, and mixtures thereof. Examples of adsorbed chemical species include ammonia, carbon dioxide, carbon monoxide, hydrogen, amines, methane, oxygen, argon, nitrogen, argon, organic dyes, polycyclic organic molecules, flavorants, small molecule therapeutics and diagnostics and combinations thereof. Examples of guest species are organic molecules with a molecular weight less than about 100 g/mol, organic molecules with a molecular weight less than about 300 g/mol, organic molecules with a molecular weight less than about 600 g/mol, organic molecules with a molecular weight greater than about 600 g/mol. In some variations, adsorbed chemical species, guest species, and space-filling agents are introduced in the metal-organic frameworks by contacting the metal-organic frameworks with a pre-selected chemical species, guest species, or space-filling agent. In another variation of the disclosure, the metal organic framework comprises an interpenetrating metal-organic framework that increases the surface area of the metal-organic framework. 
         [0072]    In still another embodiment of the disclosure, a method of forming the material set forth above is provided. 
         [0073]    The metal-organic framework is formed by combining a solution comprising a solvent and metal ions selected from the group consisting of Li + , Na + , Rb + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Ti 4+ , Zr 4+ , Ta 3+ , Cr 3+ , Mo 3+ , W 3+ , Mn 3+ , Fe 3+ , Fe 2+ , Ru 3+ , Ru 2+ , Os 3+ , Os 2+ , Co 3+ , Co 2+ , Ni 2+ , Ni + , Pd 2+ , Pd + , Pt 2+ , Pt + , Cu 2+ , Cu + , Au + , Zn 2+ , Al 3+ , Ga 3+ , In 3+ , Si 4+ , Si 2+ , Ge 4+ , Ge 2+ , Sn 4+ , Sn 2+ , Bi 5+ , Bi 3+ , and combinations thereof with a multidentate linking ligand to form a percursor bMOF. The multidentate linking ligand can comprise two or more carboxylates or anions of parent compounds selected from the group consisting of citric acid, malic acid, tartaric acid, retinoic acid, pantothenic acid, folic acid, nicitinic acid, oxalic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, alpha-linoleic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, and docosahexaenoic acid. 
         [0074]    The bMOFs of the disclosure can be formed by using any of Schemes I or II. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a nontoxic metal cation. In this embodiment, the linking moiety is shown as being a terephthalic acid or derivative thereof. Using the method of scheme I, a framework as set forth in Formula X, can be generated: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein M is a nontoxic metal cation. In this embodiment, the linking moiety is shown as being a trimesic acid or a derivative thereof (n is 1, 2 or 3). 
         [0075]    The metal-organic framework used in the disclosure optionally further comprises a non-linking ligand. In a variation, the non-linking ligand is selected from the group consisting of O 2   − , sulfate, nitrate, nitrite, sulfite, bisulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, diphosphate, triphosphate, phosphite, chloride, chlorate, bromide, bromate, iodide, iodate, carbonate, bicarbonate, sulfide, hydrogen sulphate, selenide, selenate, hydrogen selenate, telluride, tellurate, hydrogen tellurate, nitride, phosphide, arsenide, arsenate, hydrogen arsenate, dihydrogen arsenate, antimonide, antimonate, hydrogen antimonate, dihydrogen antimonate, fluoride, boride, borate, hydrogen borate, perchlorate, chlorite, hypochlorite, perbromate, bromite, hypobromite, periodate, iodite, hypoiodite; and combinations thereof. 
         [0076]    In one variation of the disclosure, the one or more ligands are removed by heating the precursor MOF. Typically, in this variation, the precursor MOF is heated to a temperature from about 30° C. to about 300° C. In another variation, the one or more ligands are removed by exposing the precursor MOF to a vacuum. Typically, the vacuum is characterized by having a pressure less than 10 −3  torr. In other variations, from about 10 −5  torr to about 700 torr. In still another variation of the disclosure, the one or more ligands are removed by simultaneously heating the precursor MOF and by exposing the precursor MOF to a vacuum. In still another variation, the solution used in the method of the disclosure may also include space-filling agents. Examples of suitable space-filling agents are set forth above. In a refinement of each of these variations, one or more ligands of the precursor MOF may be exchanged with another ligand or ligands that are more easily removed by subsequent heating and/or exposure to a vacuum. 
         [0077]    In another aspect, the framework set forth above may include an interpenetrating framework that increases the surface area of the framework. Although the frameworks of the disclosure may advantageously exclude such interpenetration, there are circumstances when the inclusion of an interpenetrating framework may be used to increase the surface area. 
         [0078]    The frameworks of the disclosure can be used as sorption devices in vitro or in vivo. Sorption is a general term that refers to a process resulting in the association of atoms or molecules with a target material. Sorption includes both adsorption and absorption. Absorption refers to a process in which atoms or molecules move into the bulk of a porous material, such as the absorption of water by a sponge. Adsorption refers to a process in which atoms or molecules move from a bulk phase (that is, solid, liquid, or gas) onto a solid or liquid surface. The term adsorption may be used in the context of solid surfaces in contact with liquids and gases. Molecules that have been adsorbed onto solid surfaces are referred to generically as adsorbates, and the surface to which they are adsorbed as the substrate or adsorbent. Adsorption is usually described through isotherms, that is, functions which connect the amount of adsorbate on the adsorbent, with its pressure (if gas) or concentration (if liquid). In general, desorption refers to the reverse of adsorption, and is a process in which molecules adsorbed on a surface are transferred back into a bulk phase. 
         [0079]    The following non-limiting examples illustrate the various embodiments of the disclosure. Those skilled in the art will recognize many variations that are within the spirit of the disclosure and scope of the claims. 
       EXAMPLES 
       [0080]    One (1)-dimensional, 2D- and 3D-environmentally friendly metal organic frameworks (efMOFs or bMOFs) of the disclosure have been synthesized and characterized by PXRD, X-ray signal crystal determinations and TGA. For example, the following synthetic routes can be used to generate certain species of the compositions of the disclosure: 
         [0081]    (a) Synthesis of 1D-efMOF: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0082]    (b) Synthesis of 2D-efMOF: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0083]    (c) Synthesis of 3D-efMOF: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0084]      FIG. 1  shows the characterization of Mg 3 (citrate) 2 (H 2 O) 6 .8H 2 O and Ca(MaI).2H 2 O.  FIG. 2  shows the characterization of Ca 3 (citrate) 2 (H 2 O) 2 .8H 2 O and Ca(Tar)(H 2 O) 2 .2H 2 O. 
         [0085]    MgBDC-1. A solid mixture of terephthalic acid (H2BDC, 240 mg) and magnesium nitrate hexahydrate Mg(NO 3 ) 2 .6H 2 O (128 mg) was dissolved in N,N-diethylformamide (13 mL) and 2.0 M aqueous HNO 3  solution (40 μL) in a 20-mL vial. 60 μL diisopropylamine and 2 mL DEF was mixed in a 4-mL vial. The 4-mL vial was placed in the 20-mL vial to allow diffusion. The 20-mL vial was capped and placed in an isothermal oven at 85° C. for 72 h.  FIG. 3  shows a framework of MgBDC-1. 
         [0086]    MgDHBDC-1. A solid mixture of 2,5-dihydroxyterephthalic acid (H2DHBDC, 40 mg) and magnesium nitrate hexahydrate Mg(NO 3 ) 2 .6H 2 O (150 mg) was dissolved in a mixture of N,N-diethylformamide (8 mL), distilled water (1 mL) and 2.0 M aqueous HNO 3  solution (20 μL) in a 20-mL vial. 20 μL diisopropylamine and 2 mL N,N-diethylformamide was mixed in a 4-mL vial. The 4-mL vial was placed in the 20-mL vial to allow diffusion. The 20-mL vial was capped and placed in an isothermal oven at 65° C. for 60 days.  FIG. 4  shows a framework of MgDHBD-1. 
         [0087]    MgOBA-1. A solid mixture of 4,4′-oxybis(benzoic acid) (H 2 OBA, 50.0 mg) and magnesium nitrate hexahydrate Mg(NO 3 ) 2 .6H2O (10.0 mg) was dissolved in N,N-dimthylformamide (5 mL) in a 20-mL vial. 20 μL diisopropylamine and 2 mL N,N-dimthylformamide was mixed in a 4-mL vial. The 4-mL vial was placed in the 20-mL vial to allow diffusion. The 20-mL vial was capped and placed in an isothermal oven at 65° C. for 10 days.  FIG. 5  shows a framework of MgOBA-1. 
         [0088]    MgBTC-1. A solid mixture of trimesic acid (H3BTC, 50.0 mg) and magnesium nitrate hexahydrate Mg(NO 3 ) 2 .6H 2 O (150.0 mg) was dissolved in a mixture of N,N-diethylformamide (5 mL), ethanol (3 mL) and 2-ethyl-1-hexanol (2 mL) in a 20-mL vial. The vial was capped and placed in an isothermal oven at 85° C. for 3 days.  FIG. 6  shows a framework of MgBTC-1. 
         [0089]    MgBTB-1. A solid mixture of 1,3,5-tri(4′-carboxy-4,4′-biphenyl)benzene (H3BTB, 43.5 mg) and magnesium acetate tetrahydrate Mg(OAc) 2 .4H 2 O (5.0 mg) was dissolved in a mixture of N,N-dimethylacetatmide (3 mL) and dimethylamine (20 μL) in a 4-mL vial. The vial was capped and placed in an isothermal oven at 120° C. for 3 days.  FIG. 7  shows a framework of MgBTB-1. 
         [0090]    MgBTB-2. A solid mixture of 4,4′,4″-benzene-1,3,5-triyl-tri-benzoic acid (H3BTB, 10.0 mg) and magnesium nitrate hexahydrate Mg(NO 3 ) 2 .6H 2 O (6.0 mg) was dissolved in a mixture of N,N-diethylformamide (2.5 mL) and distilled water (0.50 mL) in a 4-mL vial. The vial was capped and placed in an isothermal oven at 100° C. for 7 days.  FIG. 8  shows a framework of MgBTB-2. 
         [0091]    MgBTB-3. A solid mixture of 4,4′,4″-benzene-1,3,5-triyl-tri-benzoic acid (H3BTB, 10.0 mg) and magnesium acetate tetrahydrate Mg(OAc) 2 .4H 2 O (5.0 mg) was dissolved in a mixture of N-methylpyrrolidone (2 mL) and distilled water (1 mL) in a 20-mL vial. 20 μL triethylamine and 2 mL N-methylpyrrolidone was mixed in a 4-mL vial. The 4-mL vial was placed in the 20-mL vial to allow diffusion. The 20-mL vial was capped and placed in an isothermal oven at 65° C. for 7 days.  FIG. 9  shows a framework of MgBTB-3. 
         [0092]    MgBTB-4. A solid mixture of 4,4′,4″-benzene-1,3,5-triyl-tri-benzoic acid (H3BTB, 30.0 mg) and magnesium acetate tetrahydrate Mg(OAc) 2 .4H 2 O (40.0 mg) was dissolved in a mixture of N,N-diethylformamide (10 mL) and 2.0 M aqueous HNO3 solution (120 μL) in a 20-mL vial. 10 μL N,N-diisopropylamine and 2 mL N,N-diethylformamide was mixed in a 4-mL vial. The 4-mL vial was placed in the 20-mL vial to allow diffusion. The 20-mL vial was capped and placed in an isothermal oven at 65° C. for 7 days.  FIG. 10  shows a framework of MgBTB-5. 
         [0093]    MgBBC-1. A solid mixture of 4,4′,4″-benzene-1,3,5-triyl-tri-biphenylcarboxylic acid (H3BBC, 30.0 mg) and magnesium nitrate hexahydrate Mg(NO 3 ) 2 .6H 2 O (4.0 mg) was dissolved in a mixture of N,N-diethylformamide (1.5 mL), distilled water (0.30 mL) and 2M aqueous HNO 3  solution (20 μL) in a 4-mL vial. The vial was capped and placed in an isothermal oven at 100° C. for 5 days.  FIG. 11  shows a framework of MgBBC-1. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE A 
               
             
             
               
                   
               
               
                 Summary of Magnesium based edible MOF structures 
               
             
          
           
               
                 Compound 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Name 
                 Space group 
                 a(Å) 
                 b(Å) 
                 c(Å) 
                 α(°) 
                 β(°) 
                 γ(°) 
                 Dimension 
               
               
                   
               
             
          
           
               
                 MgBDC-1 
                 C2/c 
                 39.79 
                 9.04 
                 18.58 
                 90.00 
                 117.19 
                 90.00 
                 3D 
               
               
                 MgDHBDC-1 
                 R-3 
                 27.16 
                 27.16 
                 9.25 
                 90.00 
                 90.00 
                 120.00 
                 3D 
               
               
                 MgOBA-1 
                 P2(1)/n 
                 18.33 
                 20.34 
                 24.52 
                 90.00 
                 90.00 
                 90.00 
                 2D 
               
               
                 MgBTC-1 
                 P2(1)/3 
                 14.49 
                 14.49 
                 14.49 
                 90.00 
                 90.00 
                 90.00 
                 3D 
               
               
                 MgBTB-1 
                 P21/c 
                 12.45 
                 25.80 
                 27.48 
                 90.00 
                 99.36 
                 90.00 
                 2D 
               
               
                 MgBTB-2 
                 R-3 
                 38.38 
                 38.38 
                 47.01 
                 90.00 
                 90.00 
                 120.00 
                 3D 
               
               
                 MgBTB-3 
                 R-3 
                 39.60 
                 39.60 
                 22.79 
                 90.00 
                 90.00 
                 120.00 
                 3D 
               
               
                 MgBTB-4 
                 C2/c 
                 46.28 
                 38.69 
                 33.24 
                 90.00 
                 94.19 
                 90.00 
                 3D 
               
               
                 MgBBC-1 
                 C2/c 
                 41.01 
                 24.05 
                 15.23 
                 90.00 
                 95.02 
                 90.00 
                 2D 
               
               
                   
               
             
          
         
       
     
         [0094]    Although a number of embodiments and features have been described above, it will be understood by those skilled in the art that modifications and variations of the described embodiments and features may be made without departing from the teachings of the disclosure or the scope of the disclosure as defined by the appended claims.