Pore Environment Effects on Catalytic Cyclohexane Oxidation in Expanded Fe<sub>2</sub>(dobdc) Analogues

Xiao, Dianne J.; Oktawiec, Julia; Milner, Phillip J.; Long, Jeffrey R.

doi:10.1021/jacs.6b08417

Cited by 144 publications

(130 citation statements)

References 79 publications

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“…A synthetic route very similar to that previously reported 54 was followed. A 20 mL scintillation vial was charged with H4dotpdc (4,4''-dihydroxy-[1,1':4′,1''-terphenyl]-3,3''-dicarboxylic acid) (35.0 mg, 0.103 mmol, 1.00 equiv) and Mg(NO3)2•6H2O (64.0 mg, 0.250 mmol, 2.50 equiv).…”

Section: Synthesis Of Mg2(dotpdc)mentioning

confidence: 98%

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Forse

Milner²,

Lee³

et al. 2018

Preprint

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The widespread deployment of carbon capture and sequestration as a climate change mitigation strategy could be facilitated by the development of more energy-efficient adsorbents. Diamine-appended metal-organic frameworks of the type diamine-M2(dobpdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobpdc 4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) have shown promise for carbon capture applications, although questions remain regarding the molecular mechanisms of CO2 uptake in these materials. Here, we leverage the crystallinity and tunability of this class of frameworks to perform a comprehensive study of CO2 chemisorption. Using multinuclear nuclear magnetic resonance (NMR) spectroscopy experiments and van der Waals-corrected density functional theory (DFT) calculations for thirteen diamine-M2(dobpdc) variants, we demonstrate that the canonical CO2 chemisorption products-ammonium carbamate chains and carbamic acid pairs-can be readily distinguished, and that ammonium carbamate chain formation dominates for diamine-Mg2(dobpdc) materials. In addition, we elucidate a new chemisorption mechanism in the material dmpn-Mg2(dobpdc) (dmpn = 2,2-dimethyl-1,3-diaminopropane), which involves formation of a 1:1 mixture of ammonium carbamate and carbamic acid and accounts for the unusual adsorption properties of this material. Finally, we show that the presence of water plays an important role in directing the mechanisms for CO2 uptake in diamine-M2(dobpdc) materials. Overall, our combined NMR and DFT approach enables a thorough depiction and understanding of CO2 adsorption within diamine-M2(dobpdc) compounds, which may aid similar studies in other amine-functionalized adsorbents in the future.

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Section: Synthesis Of Mg2(dotpdc)mentioning

confidence: 98%

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Forse

Milner²,

Lee³

et al. 2018

Preprint

Self Cite

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“…The surface wettability of heterogeneous catalysts can profoundly affect their activity and selectivity by modulating their interactions with reactants and products . In 2016, Jiang and coworkers reported that hydrophobic modification can enhance catalytic performance.…”

Section: Potential Applications Of Hydrophobic Mofs and Their Compositesmentioning

confidence: 99%

Hydrophobic Metal–Organic Frameworks

et al. 2019

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formed from organic ligands and metal cations. [1][2][3][4][5][6][7][8][9][10] They are typically synthesized under mild conditions via coordinationdirected self-assembly processes and are also known as metal-organic coordination networks and porous coordination polymers. [11][12][13][14] Due to their high surface areas, large porosity, tunable pore sizes, and functionalities, MOFs have prospective applications in fields such as gas storage/separation, sensing or recognition, proton conduction, and magnetism. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] However, the advantageous unique structural features of even some of the best-performing MOFs are readily degraded because of their high moisture sensitivity, which may limit their practical applications. [29][30][31][32] Consequently, there is an ongoing search for highly hydrophobic, porous, sorbent materials to be employed in various large-scale applications in industry such as oil spill cleanup, hydrocarbon storage/separation, or water purification. [33][34][35][36][37] Many academics, industrial scientists, and engineers have therefore conducted research on the fabrication of superhydrophobic surfaces, which involves hydrophobic surface modification and creating surface roughness on the micrometer-or nanoscale. Hydrophobic surfaces are defined as substrates with an apparent contact angle greater than 90° with respect to water. On superhydrophobic materials, water droplets have contact angles above 150° and show very low adhesion because the drops partially rest on an air cushion. The surface energy and roughness govern the wettability of hydrophobic surfaces. In general, lower surface energies and higher roughness are associated with larger contact angles, lower contact angle hysteresis, and robust superhydrophobicity. Because of their ultralow surface energies (10-20 mN m −1 ), alkyl-based or fluorinated compounds are commonly used as hydrophobic modifiers to prepare surfaces with high intrinsic contact angles (>90°). [33][34][35][36][37][38][39][40][41][42] Recently, few methods have been developed for synthesizing hydrophobic MOFs including both pristine and composite systems. This review offers a comprehensive overview of the state of the art in hydrophobic MOF synthesis and the field's challenges and opportunities. Various synthetic strategies for preparing hydrophobic MOFs and their composites are introduced. We discuss the basics of wetting and critical challenges in the characterization of these hydrophobic materials. The potential applications of hydrophobic MOFs and related Metal-organic frameworks (MOFs) have diverse potential applications in catalysis, gas storage, separation, and drug delivery because of their nanoscale periodicity, permanent porosity, channel functionalization, and structural diversity. Despite these promising properties, the inherent structural features of even some of the best-performing MOFs make them moisture-sensitive and unstable in aqueous media, limiting their practical usefulness. This problem could be ...

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“…Long et al investigatedi soreticular Fe II -based MOFs for the oxidation of simple hydrocarbons ( Figure 6). [42] Fe-MOF-74 (based on 2,5-dioxido-1,4-benzenedicarboxylate (dobdc) linkers;p ore diameter of 8 ), displayed no activity towards the oxidation of cyclohexane (8)u sing 5 as the terminal oxidant (van derW aals volumeo f5 is 221 3 ;d iameter = 7.5 assuming 5 is approximately spherical). For comparison, Fe-MOF-74 did show activity in ethane oxidationt og enerate ethanol using N 2 Oa st he terminal oxidant.…”

Section: Isoreticular Catalystmaterialsmentioning

confidence: 99%

“…Modified with permission from Ref. [42].C opyright 2016, the American Chemical Society. through solvothermals ynthesis.…”

Section: Differently-sized Mof Crystallitesmentioning

confidence: 99%

In Operando Analysis of Diffusion in Porous Metal‐Organic Framework Catalysts

Gao

Cardenal

Wang

et al. 2018

Chemistry A European J

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The potential to exert atomistic control over the structure of site‐isolated catalyst sites, as well as the topology and chemical environment of interstitial pore spaces, has inspired efforts to apply porous metal‐organic frameworks (MOFs) as catalysts for fine chemical synthesis. In analogy to enzyme‐catalyzed reactions, MOF catalysts have been proposed as platforms in which substrate confinement could be used to achieve chemo‐ and stereoselectivities that are orthogonal to solution‐phase catalysts. In order to leverage the tunable pore topology of MOFs to impact catalyst selectivity, catalysis must proceed at interstitial catalyst sites, rather than at solvent‐exposed interfacial sites. This Minireview addresses challenges inherent to interstitial MOF catalysis by 1) describing the diffusional processes available to sorbates in porous materials, 2) discussing critical factors that impact the diffusion rate of substrates in porous materials, and 3) presenting in operando experimental strategies to assess the relative rates of substrate diffusion and catalyst turnover in MOF catalysis. It is anticipated that the continued development of in operando tools to evaluate substrate diffusion in porous catalysts will advance the application of these materials in fine chemical synthesis.

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Pore Environment Effects on Catalytic Cyclohexane Oxidation in Expanded Fe₂(dobdc) Analogues

Cited by 144 publications

References 79 publications

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Hydrophobic Metal–Organic Frameworks

In Operando Analysis of Diffusion in Porous Metal‐Organic Framework Catalysts

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Pore Environment Effects on Catalytic Cyclohexane Oxidation in Expanded Fe2(dobdc) Analogues

Cited by 144 publications

References 79 publications

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Hydrophobic Metal–Organic Frameworks

In Operando Analysis of Diffusion in Porous Metal‐Organic Framework Catalysts

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Pore Environment Effects on Catalytic Cyclohexane Oxidation in Expanded Fe₂(dobdc) Analogues