Ring-Opening Reactions within Porous Metal−Organic Frameworks

Two new metal−organic framework (MOF) structures, IRMOF-3b and -3c, were prepared by ring-opening reaction of 1,3-propanesultone and 2-methylaziridine with an amine functionalized MOF, IRMOF-3. The new structures are permanently functionalized with covalently linked sulfonate and alkyamine units, respectively. The underlying framework structure is retained after reaction as confirmed by powder X-ray diffraction. The high porosity of IRMOF-3 is also maintained, as evidenced by nitrogen adsorption experiments, which yield Brunauer−Emmett−Teller (BET) surface areas of 1380 and 530 m2 g−1 compared to 2040 m2 g−1 in the parent material. Ring-opening reactions provide a versatile route to irreversible binding of a range of functionalities that are otherwise difficult to access in MOFs

Crystalline Covalent Organic Frameworks with Hydrazone Linkages

Condensation of 2,5-diethoxyterephthalohydrazide with 1,3,5-triformylbenzene or 1,3,5-tris(4-formylphenyl)benzene yields two new covalent organic frameworks, COF-42 and COF-43, in which the organic building units are linked through hydrazone bonds to form extended two-dimensional porous frameworks. Both materials are highly crystalline, display excellent chemical and thermal stability, and are permanently porous. These new COFs expand the scope of possibilities for this emerging class of porous materials

A Crystalline Imine-Linked 3-D Porous Covalent Organic Framework

A Crystalline Imine-Linked 3-D Porous Covalent Organic Framewor

A Crystalline Imine-Linked 3-D Porous Covalent Organic Framework

A Crystalline Imine-Linked 3-D Porous Covalent Organic Framewor

Synthesis, Structure, and Carbon Dioxide Capture Properties of Zeolitic Imidazolate Frameworks

Zeolites are one of humanity’s most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications.Recently, it was recognized that the Si−O−Si preferred angle in zeolites (145°) is coincident with that of the bridging angle in the M−Im−M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures.In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link−link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example.The chemical and thermal stability of ZIFs permit many applications, such as the capture of CO2 and its selective separation from industrially relevant gas mixtures. Currently, ZIFs are the best porous materials for the selective capture of CO2; furthermore, they show exceptionally high capacity for CO2 among adsorbents operating by physisorption. The stability of ZIFs has also enabled organic transformations to be carried out on the crystals, yielding covalently functionalized isoreticular structures wherein the topology, crystallinity, and porosity of the ZIF structure are maintained throughout the reaction process. These reactions, being carried out on macroscopic crystals that behave as single molecules, have enabled the realization of the chemist’s dream of using “crystals as molecules”, opening the way for the application of the extensive library of organic reactions to the functionalization of useful extended porous structures

Metal Insertion in a Microporous Metal−Organic Framework Lined with 2,2′-Bipyridine

Reaction of AlCl3·6H2O with 2,2′-bipyridine-5,5′-dicarboxylic acid (H2bpydc) affords Al(OH)(bpydc) (1, MOF-253), the first metal−organic framework with open 2,2′-bipyridine (bpy) coordination sites. The material displays a BET surface area of 2160 m2/g and readily complexes metals to afford, for example, 1·xPdCl2 (x = 0.08, 0.83) and 1·0.97Cu(BF4)2. EXAFS spectroscopy performed on 1·0.83PdCl2 reveals the expected square planar coordination geometry, matching the structure of the model complex (bpy)PdCl2. Significantly, the selectivity factor for binding CO2 over N2 under typical flue gas conditions is observed to increase from 2.8 in 1 to 12 in 1·0.97Cu(BF4)2

Isoreticular Expansion of Metal–Organic Frameworks with Triangular and Square Building Units and the Lowest Calculated Density for Porous Crystals

The concept and occurrence of isoreticular (same topology) series of metal–organic frameworks (MOFs) is reviewed. We describe the preparation, characterization, and crystal structures of three new MOFs that are isoreticular expansions of known materials with the tbo (Cu3(4,4′,4″-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate)2, MOF-399) and pto topologies (Cu3(4,4′,4″-(benzene-1,3,5-triyl-tribenzoate)2, MOF-143; Cu3(4,4′,4″-(triazine-2,4,6-triyl-tris(benzene-4,1-diyl))tribenzoate)2, MOF-388). One of these materials (MOF-399) has a unit cell volume 17 times larger than that of the first reported material isoreticular to it, and has the highest porosity (94%) and lowest density (0.126 g cm–3) of any MOFs reported to date

Solid State Multicolor Emission in Substitutional Solid Solutions of Metal–Organic Frameworks

Preparing crystalline materials that produce tunable organic-based multicolor emission is a challenge due to the inherent inability to control the packing of organic molecules in the solid state. Utilizing multivariate, high-symmetry metal–organic frameworks, MOFs, as matrices for organic-based substitutional solid solutions allows for the incorporation of multiple fluorophores with different emission profiles into a single material. By combining nonfluorescent links with dilute mixtures of red, green, and blue fluorescent links, we prepared zirconia-type MOFs and found that the bulk materials exhibit features of solution-like fluorescence. Our study found that MOFs with a fluorophore link concentration of around 1 mol % exhibit fluorescence with decreased inner filtering, demonstrated by changes in spectral profiles, increased quantum yields, and lifetime dynamics expected for excited-state proton-transfer emitters. Our findings enabled us to prepare organic-based substitutional solid solutions with tunable chromaticity regulated only by the initial amounts of fluorophores. These materials emit multicolor and white light with high quantum yields (∼2–14%), high color-rendering indices (>93), long shelf life, and superb hydrolytic stability at ambient conditions

Solid State Multicolor Emission in Substitutional Solid Solutions of Metal–Organic Frameworks

Preparing crystalline materials that produce tunable organic-based multicolor emission is a challenge due to the inherent inability to control the packing of organic molecules in the solid state. Utilizing multivariate, high-symmetry metal–organic frameworks, MOFs, as matrices for organic-based substitutional solid solutions allows for the incorporation of multiple fluorophores with different emission profiles into a single material. By combining nonfluorescent links with dilute mixtures of red, green, and blue fluorescent links, we prepared zirconia-type MOFs and found that the bulk materials exhibit features of solution-like fluorescence. Our study found that MOFs with a fluorophore link concentration of around 1 mol % exhibit fluorescence with decreased inner filtering, demonstrated by changes in spectral profiles, increased quantum yields, and lifetime dynamics expected for excited-state proton-transfer emitters. Our findings enabled us to prepare organic-based substitutional solid solutions with tunable chromaticity regulated only by the initial amounts of fluorophores. These materials emit multicolor and white light with high quantum yields (∼2–14%), high color-rendering indices (>93), long shelf life, and superb hydrolytic stability at ambient conditions