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

Metal–Organic Frameworks for Separations

Kenji Sumida, David L. Rogow, Jarad A. Mason, Thomas M. McDonald, Eric D. Bloch, Zoey R. Herm, Tae-Hyun Bae, Jeffrey R. Long

Carbon Dioxide Capture in Metal–Organic Frameworks

New materials capable of storing hydrogen at high gravimetric and volumetric densities are required if hydrogen is to be widely employed as a clean alternative to hydrocarbon fuels in cars and other mobile applications. With exceptionally high surface areas and chemically-tunable structures, microporous metal–organic frameworks have recently emerged as some of the most promising candidate materials. In this critical review we provide an overview of the current status of hydrogen storage within such compounds. Particular emphasis is given to the relationships between structural features and the enthalpy of hydrogen adsorption, spectroscopic methods for probing framework–H2 interactions, and strategies for improving storage capacity (188 references).

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Hydrogen storage in metal–organic frameworks

Metal–organic frameworks (MOFs) are a unique class of crystalline solids comprised of metal cations (or metal clusters) and organic ligands that have shown promise for a wide variety of applications Over the past 15 years, research and development of these materials have become one of the most intensely and extensively pursued areas A very interesting and well-investigated topic is their optical emission properties and related applications Several reviews have provided a comprehensive overview covering many aspects of the subject up to 2011 This review intends to provide an update of work published since then and focuses on the photoluminescence (PL) properties of MOFs and their possible utility in chemical and biological sensing and detection The spectrum of this review includes the origin of luminescence in MOFs, the advantages of luminescent MOF (LMOF) based sensors, general strategies in designing sensory materials, and examples of various applications in sensing and detection

Luminescent metal–organic frameworks for chemical sensing and explosive detection

Hydrogen Storage in Metal–Organic Frameworks

We demonstrate by experimental and theoretical studies that the impregnation of various metal ions such as Li+, Mg2+, Ca2+, Co2+, and Ni2+ in the pores of an anionic MOF, [Zn3(TCPT)2(HCOO)][NH2(CH3)2] (SNU-100′) significantly enhances isosteric heat, selectivity, and uptake capacity of the CO2 adsorption in the MOF. Due to the electrostatic interactions between CO2 and the extra-framework metal ions, the isosteric heats of CO2 adsorption are increased to 37.4–34.5 kJ mol−1 and the adsorption selectivities of CO2 over N2 at room temperature are increased to 40.4–31.0, compared with those (29.3 kJ mol−1 and 25.5, respectively) of the parent MOF (SNU-100′) containing [NH2(CH3)2]+ cations.

Enhanced isosteric heat, selectivity, and uptake capacity of CO2 adsorption in a metal-organic framework by impregnated metal ions

Stepwise and hysteretic sorption of N2, O2, CO2, and H2 gases in a porous metal–organic framework [Zn2(BPnDC)2(bpy)]

The porous metal-organic framework (MOF) {[Zn(2)(TCPBDA)(H(2)O)(2)]⋅30 DMF⋅6 H(2)O}(n) (SNU-30; DMF = N,N-dimethylformamide) has been prepared by the solvothermal reaction of N,N,N',N'-tetrakis(4-carboxyphenyl)biphenyl-4,4'-diamine (H(4)TCPBDA) and Zn(NO(3))(2)⋅6 H(2)O in DMF/tBuOH. The post-synthetic modification of SNU-30 by the insertion of 3,6-di(4-pyridyl)-1,2,4,5-tetrazine (bpta) affords single-crystalline {[Zn(2)(TCPBDA)(bpta)]⋅23 DMF⋅4 H(2)O}(n) (SNU-31 SC), in which channels are divided by the bpta linkers. Interestingly, unlike its pristine form, the bridging bpta ligand in the MOF is bent due to steric constraints. SNU-31 can be also prepared through a one-pot solvothermal synthesis from Zn(II), TCPBDA(4-), and bpta. The bpta linker can be liberated from this MOF by immersion in N,N-diethylformamide (DEF) to afford the single-crystalline SNU-30 SC, which is structurally similar to SNU-30. This phenomenon of reversible insertion and removal of the bridging ligand while preserving the single crystallinity is unprecedented in MOFs. Desolvated solid SNU-30' adsorbs N(2), O(2), H(2), CO(2), and CH(4) gases, whereas desolvated SNU-31' exhibits selective adsorption of CO(2) over N(2), O(2), H(2), and CH(4), thus demonstrating that the gas adsorption properties of MOF can be modified by post-synthetic insertion/removal of a bridging ligand.

Post-synthetic reversible incorporation of organic linkers into porous metal-organic frameworks through single-crystal-to-single-crystal transformations and modification of gas-sorption properties.

A doubly interpenetrating porous metal-organic framework (SNU-77) has been synthesized from the solvothermal reaction of the ex- tended carboxylic acid tris(4'-carboxy- biphenyl)amine (H3TCBPA) and Zn- A3)2·6H2 Oi nN,N-dimethylacet- A (DMA). SNU-77 undergoes single-crystal-to-single-crystal transfor- mations during various activation pro- cesses, such as room-temperature evac- uation, supercritical CO2 drying, and high temperature evacuation, to afford SNU-77R, SNU-77S, and SNU-77H, respectively. These guest-free MOFs exhibited different fine structures with different window shapes and different effective window sizes at room temper- ature. Variable-temperature synchro- tron single-crystal X-ray analyses reveal that the guest-free structure is also affected by changes in tempera- ture. Despite the different fine struc- tures, SNU-77R, SNU-77S, and SNU- 77H show similar gas sorption proper- ties due to the nonbreathing nature of the framework and an additional struc- tural change upon cooling to cryogenic gas sorption temperature. SNU-77H exhibits a large surface area (BET, 3670 m 2 g � 1 ), a large pore volume (1.52 cm 3 g � 1 ), and exceptionally high uptake capacities for N2 ,H 2 ,O 2 ,C O 2, and CH4 gases.

Hye Jeong Park

Papers

Hydrogen Storage in Metal–Organic Frameworks

Enhanced isosteric heat, selectivity, and uptake capacity of CO2 adsorption in a metal-organic framework by impregnated metal ions

Stepwise and hysteretic sorption of N2, O2, CO2, and H2 gases in a porous metal–organic framework [Zn2(BPnDC)2(bpy)]

Post-synthetic reversible incorporation of organic linkers into porous metal-organic frameworks through single-crystal-to-single-crystal transformations and modification of gas-sorption properties.

A Highly Porous Metal–Organic Framework: Structural Transformations of a Guest‐Free MOF Depending on Activation Method and Temperature