Postsynthetic Modification of a Metal–Organic Framework for Stabilization of a Hemiaminal and Ammonia Uptake

Morris, William,Doonan, Christian J.,Yaghi, Omar M. American Chemical Society 2011 Inorganic chemistry Vol.50 No.15

<P>In our study, we show by solid-state <SUP>15</SUP>N NMR measurements that an important zirconium metal–organic framework (UiO-66) with amino-functionalized links is composed of a mixture of amino and −NH<SUB>3</SUB><SUP>+</SUP>Cl<SUP>–</SUP> salt functionalities rather than all amino functionality to give a composition of Zr<SUB>6</SUB>O<SUB>4</SUB>(OH)<SUB>4</SUB>(BDC-NH<SUB>2</SUB>)<SUB>4</SUB>(BDC-NH<SUB>3</SUB><SUP>+</SUP>Cl<SUP>–</SUP>)<SUB>2</SUB> (UiO-66-A). UiO-66-A was postsynthetically modified to form a mixture of three functionalities, where the hemiaminal functionality is the majority species in UiO-66-B and aziridine is the majority functionality in UiO-66-C. UiO-66-A–C are all porous with surface areas ranging from 780 to 820 m<SUP>2</SUP>/g and have chemical stability, as evidenced by reversible ammonia uptake and release showing capacities ranging from 134 to 193 cm<SUP>3</SUP>/g.</P><P>Zr<SUB>6</SUB>O<SUB>4</SUB>(OH)<SUB>4</SUB>(BDC-NH<SUB>2</SUB>)<SUB>4</SUB>(BDC-NH<SUB>3</SUB><SUP>+</SUP>Cl<SUP>−</SUP>)<SUB>2</SUB> (UiO-66-A), a crystalline porous framework, is synthesized as a result of the reaction of ZrCl<SUB>4</SUB> and 2-aminoterephthalic acid (H<SUB>2</SUB>BDCNH<SUB>2</SUB>). UiO-66-A was postsynthetically modified to form a mixture of three functionalities, where the hemiaminal functionality is the majority species in UiO-66-B and aziridine is the majority functionality in UiO-66-C. Furthermore, investigation of ammonia adsorption in UiO-66-A−C shows reversible ammonia adsorption in each framework, with the highest uptake observed in UiO-66-C.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2011/inocaj.2011.50.issue-15/ic200744y/production/images/medium/ic-2011-00744y_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic200744y'>ACS Electronic Supporting Info</A></P>

Metal–Organic Frameworks of Vanadium as Catalysts for Conversion of Methane to Acetic Acid

Phan, Anh,Czaja, Alexander U.,Gá,ndara, Felipe,Knobler, Carolyn B.,Yaghi, Omar M. American Chemical Society 2011 Inorganic chemistry Vol.50 No.16

<P>A catalytic system combining the high activity of homogeneous catalysts and the ease of use of heterogeneous catalysts for methane activation is reported. The vanadium-containing metal–organic frameworks (MOFs) MIL-47 and MOF-48 are found to have high catalytic activity and chemical stability. They convert methane selectively to acetic acid with 70% yield (490 TON) based on K<SUB>2</SUB>S<SUB>2</SUB>O<SUB>8</SUB> as an oxidant. Isotopic labeling experiments showed that two methane molecules are converted to the produced acetic acid. The MOF catalysts are reusable and remain catalytically active for several recycling steps without losing their crystalline structures.</P><P>The vanadium-containing metal−organic framework MOF-48 catalyzes the selective direct oxidation of methane to acetic acid. The yield is 49% (based on K<SUB>2</SUB>S<SUB>2</SUB>O<SUB>8</SUB> as an oxidant), 490 TON, at 80 °C in a trifluoroacetic acid solvent.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2011/inocaj.2011.50.issue-16/ic201396m/production/images/medium/ic-2011-01396m_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic201396m'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic201396m'>ACS Electronic Supporting Info</A></P>

Chemical Environment Control and Enhanced Catalytic Performance of Platinum Nanoparticles Embedded in Nanocrystalline Metal–Organic Frameworks

Choi, Kyung Min,Na, Kyungsu,Somorjai, Gabor A.,Yaghi, Omar M. American Chemical Society 2015 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.137 No.24

<P>Chemical environment control of the metal nanoparticles (NPs) embedded in nanocrystalline metal–organic frameworks (nMOFs) is useful in controlling the activity and selectivity of catalytic reactions. In this report, organic linkers with two functional groups, sulfonic acid (−SO<SUB>3</SUB>H, S) and ammonium (−NH<SUB>3</SUB><SUP>+</SUP>, N), are chosen as strong and weak acidic functionalities, respectively, and then incorporated into a MOF [Zr<SUB>6</SUB>O<SUB>4</SUB>(OH)<SUB>4</SUB>(BDC)<SUB>6</SUB> (BDC = 1,4-benzenedicarboxylate), termed UiO-66] separately or together in the presence of 2.5 nm Pt NPs to build a series of Pt NPs-embedded in UiO-66 (Pt⊂nUiO-66). We find that these chemical functionalities play a critical role in product selectivity and activity in the gas-phase conversion of methylcyclopentane (MCP) to acyclic isomer, olefins, cyclohexane, and benzene. Pt⊂nUiO-66-S gives the highest selectivity to C<SUB>6</SUB>-cyclic products (62.4% and 28.6% for cyclohexane and benzene, respectively) without acyclic isomers products. Moreover, its catalytic activity was doubled relative to the nonfunctionalized Pt⊂nUiO-66. In contrast, Pt⊂nUiO-66-N decreases selectivity for C<SUB>6</SUB>-cyclic products to <50% while increases the acyclic isomer selectivity to 38.6%. Interestingly, the Pt⊂nUiO-66-SN containing both functional groups gave different product selectivity than their constituents; no cyclohexane was produced, while benzene was the dominant product with olefins and acyclic isomers as minor products. All Pt⊂nUiO-66 catalysts with different functionalities remain intact and maintain their crystal structure, morphology, and chemical functionalities without catalytic deactivation after reactions over 8 h.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2015/jacsat.2015.137.issue-24/jacs.5b03540/production/images/medium/ja-2015-035409_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja5b03540'>ACS Electronic Supporting Info</A></P>

Neuroimaging of Acute Ischemic Stroke: Multimodal Imaging Approach for Acute Endovascular Therapy

Mohamad Abdalkader,James E. Siegler,Jin Soo Lee,Shadi Yaghi,Zhongming Qiu,Xiaochuan Huo,Zhongrong Miao,Bruce C.V. Campbell,Thanh N. Nguyen 대한뇌졸중학회 2023 Journal of stroke Vol.25 No.1

Advances in acute ischemic stroke (AIS) treatment have been contingent on innovations in neuroimaging. Neuroimaging plays a pivotal role in the diagnosis and prognosis of ischemic stroke and large vessel occlusion, enabling triage decisions in the emergent care of the stroke patient. Current imaging protocols for acute stroke are dependent on the available resources and clinicians’ preferences and experiences. In addition, differential application of neuroimaging in medical decision-making, and the rapidly growing evidence to support varying paradigms have outpaced guideline-based recommendations for selecting patients to receive intravenous or endovascular treatment. In this review, we aimed to discuss the various imaging modalities and approaches used in the diagnosis and treatment of AIS.

NMR and X-ray Study Revealing the Rigidity of Zeolitic Imidazolate Frameworks

Morris, William,Stevens, Caitlin J.,Taylor, R. E.,Dybowski, C.,Yaghi, Omar M.,Garcia-Garibay, Miguel A. American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.24

<P>NMR relaxation studies and spectroscopic measurements of zeolitic imidazolate framework-8 (ZIF-8) are reported. The dominant nuclear spin–lattice relaxation (<I>T</I><SUB>1</SUB>) mechanism for ZIF-8 in air arises from atmospheric paramagnetic molecular oxygen. The <SUP>13</SUP>C <I>T</I><SUB>1</SUB> measurements indicate that the oxygen interacts primarily with the imidazolate ring rather than the methyl substituent. Similar relaxation behavior was also observed in a ZIF with an unsubstituted ring, ZIF-4. Single-crystal X-ray diffraction was used to provide data for the study of the thermal ellipsoids of ZIF-8 at variable temperatures from 100 to 298 K, which further confirmed the rigid nature of this ZIF framework. These results highlight a rigid ZIF framework and are in contrast with dynamic metal–organic frameworks based on benzenedicarboxylate linking groups, for which the relaxation reflects the dynamics of the benzenedicarboxylate moiety.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-24/jp303907p/production/images/medium/jp-2012-03907p_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp303907p'>ACS Electronic Supporting Info</A></P>

Heterogeneity within Order in Crystals of a Porous Metal–Organic Framework

Choi, Kyung Min,Jeon, Hyung Joon,Kang, Jeung Ku,Yaghi, Omar M. American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.31

<P>Generally, crystals of synthetic porous materials such as metal–organic frameworks (MOFs) are commonly made up from one kind of repeating pore structure which predominates the whole material. Surprisingly, little is known about how to introduce heterogeneously arranged pores within a crystal of homogeneous pores without losing the crystalline nature of the material. Here, we outline a strategy for producing crystals of MOF-5 in which a system of meso- and macropores either permeates the whole crystal to make sponge-like crystals or is entirely enclosed by a thick crystalline microporous MOF-5 sheath to make pomegranate-like crystals. These new forms of crystals represent a new class of materials in which micro-, meso-, and macroporosity are juxtaposed and are directly linked unique arrangements known to be useful in natural systems but heretofore unknown in synthetic crystals.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-31/ja204818q/production/images/medium/ja-2011-04818q_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja204818q'>ACS Electronic Supporting Info</A></P>

Hydrogen Storage in New Metal–Organic Frameworks

Tranchemontagne, David J.,Park, Kyo Sung,Furukawa, Hiroyasu,Eckert, Juergen,Knobler, Carolyn B.,Yaghi, Omar M. American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.24

<P>Five new metal–organic frameworks (MOFs, termed MOF-324, 325, 326 and IRMOF-61 and 62) of either short linkers (pyrazolecarboxylate and pyrazaboledicarboxylate) or long and thin alkyne functionalities (ethynyldibenzoate and butadiynedibenzoate) were prepared to examine their impact on hydrogen storage in MOFs. These compounds were characterized by single-crystal X-ray diffraction, and their low-pressure and high-pressure hydrogen uptake properties were investigated. In particular, volumetric excess H<SUB>2</SUB> uptake by MOF-324 and IRMOF-62 outperforms MOF-177 up to 30 bar. Inelastic neutron-scattering studies for MOF-324 also revealed strong interactions between the organic links and hydrogen, in contrast to MOF-5 where the interactions between the Zn<SUB>4</SUB>O unit and hydrogen are the strongest. These data also show that smaller pores and polarized linkers in MOFs are indeed advantageous for hydrogen storage.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-24/jp302356q/production/images/medium/jp-2012-02356q_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp302356q'>ACS Electronic Supporting Info</A></P>

Plasmon-Enhanced Photocatalytic CO₂ Conversion within Metal–Organic Frameworks under Visible Light

Choi, Kyung Min,Kim, Dohyung,Rungtaweevoranit, Bunyarat,Trickett, Christopher A.,Barmanbek, Jesika Trese Deniz,Alshammari, Ahmad S.,Yang, Peidong,Yaghi, Omar M. American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.1

<P>Materials development for artificial photosynthesis, in particular, CO2 reduction, has been under extensive efforts, ranging from inorganic semiconductors to molecular complexes. In this report, we demonstrate a metal organic framework (MOF)-coated nanoparticle photocatalyst with enhanced CO2 reduction activity and stability, which stems from having two different functional units for activity enhancement and catalytic stability combined together as a single construct. Covalently attaching a CO2-to-CO conversion photocatalyst Re-I(CO)(3)(BPYDC)Cl, BPYDC = 2,2'-bipyridine-5,5'-dicarboxylate, to a zirconium MOF, UiO-67 (Re-n-MOF), prevents dimerization leading to deactivation. By systematically controlling its density in the framework (n = 0, 1, 2, 3, 5, 11, 16, and 24 complexes per unit cell), the highest photocatalytic activity was found for Re-3-MOF. Structural analysis of Re-MOFs suggests that a fine balance of proximity between photoactive centers is needed for cooperatively enhanced photocatalytic activity, where an optimum number of Re complexes per unit cell should reach the highest activity. Based on the structure-activity correlation of Ren-M0Fs, Rea-MOF was coated onto Ag nanocubes (AgCRe3-MOF), which spatially confined photoactive Re centers to the intensified near-surface electric fields at the surface of Ag nanocubes, resulting in a 7-fold enhancement of CO2-to-CO conversion under visible light with long-term stability maintained up to 48 h.</P>

Supercapacitors of Nanocrystalline Metal–Organic Frameworks

Choi, Kyung Min,Jeong, Hyung Mo,Park, Jung Hyo,Zhang, Yue-Biao,Kang, Jeung Ku,Yaghi, Omar M. American Chemical Society 2014 ACS NANO Vol.8 No.7

<P>The high porosity of metal–organic frameworks (MOFs) has been used to achieve exceptional gas adsorptive properties but as yet remains largely unexplored for electrochemical energy storage devices. This study shows that MOFs made as nanocrystals (nMOFs) can be doped with graphene and successfully incorporated into devices to function as supercapacitors. A series of 23 different nMOFs with multiple organic functionalities and metal ions, differing pore sizes and shapes, discrete and infinite metal oxide backbones, large and small nanocrystals, and a variety of structure types have been prepared and examined. Several members of this series give high capacitance; in particular, a zirconium MOF exhibits exceptionally high capacitance. It has the stack and areal capacitance of 0.64 and 5.09 mF cm<SUP>–2</SUP>, about 6 times that of the supercapacitors made from the benchmark commercial activated carbon materials and a performance that is preserved over at least 10000 charge/discharge cycles.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-7/nn5027092/production/images/medium/nn-2014-027092_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5027092'>ACS Electronic Supporting Info</A></P>

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

Furukawa, Hiroyasu,Go, Yong Bok,Ko, Nakeun,Park, Young Kwan,Uribe-Romo, Fernando J.,Kim, Jaheon,O’Keeffe, Michael,Yaghi, Omar M. American Chemical Society 2011 Inorganic Chemistry Vol.50 No.18

<P>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 <B>tbo</B> (Cu<SUB>3</SUB>(4,4′,4″-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate)<SUB>2</SUB>, MOF-399) and <B>pto</B> topologies (Cu<SUB>3</SUB>(4,4′,4″-(benzene-1,3,5-triyl-tribenzoate)<SUB>2</SUB>, MOF-143; Cu<SUB>3</SUB>(4,4′,4″-(triazine-2,4,6-triyl-tris(benzene-4,1-diyl))tribenzoate)<SUB>2</SUB>, 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<SUP>–3</SUP>) of any MOFs reported to date.</P><P>Syntheses of three new metal−organic frameworks (MOFs) that are isoreticular (same topology) expansions of known materials with the <B>tbo</B> and <B>pto</B> topologies are reported. 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 void fraction (94%) and lowest density (0.126 g cm<SUP>−3</SUP>) of any MOFs reported to date.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2011/inocaj.2011.50.issue-18/ic201376t/production/images/medium/ic-2011-01376t_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic201376t'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic201376t'>ACS Electronic Supporting Info</A></P>