Metal–organic frameworks (MOFs) are promising materials for storing natural gas in vehicular applications. Evaluation of these materials has focused on adsorption of pure methane, although commercial ...natural gas also contains small amounts of higher hydrocarbons such as ethane and propane, which adsorb more strongly than methane. There is, thus, a possibility that these higher hydrocarbons will accumulate in the MOF after multiple operating (adsorption/desorption) cycles, and reduce the storage capacity. To study the net effect of ethane and propane on the performance of an adsorbed natural gas (ANG) tank, we developed a mathematical model based on thermodynamics and mass balance equations that describes the state of the tank at any instant. The required inputs are the pure-component isotherms, and mixture adsorption data are calculated using the Ideal Adsorbed Solution Theory (IAST). We focused on how the “deliverable energy” provided by the ANG tank to the engine changed over 200 operating cycles for a sample of 120 MOF structures. We found that, with any MOF, the ANG tank performance monotonically declines during early operating cycles until a “cyclic steady state” is reached. We determined that the best materials when the fuel is 100% methane are not necessarily the best when the fuel includes ethane and propane. Among the materials tested, some top MOFs are MOF-143 > NU-800 > IRMOF-14 > IRMOF-20 > MIL-100 > NU-125 > IRMOF-1 > NU-111. MOF-143 is predicted to deliver 5.43 MJ L −1 of tank to the engine once the cyclic steady state is reached. The model also provided insights that can assist in future work to discover more promising adsorbent materials for natural gas storage.
We designed, synthesized, and characterized a new Zr‐based metal–organic framework material, NU‐1100, with a pore volume of 1.53 ccg−1 and Brunauer–Emmett–Teller (BET) surface area of 4020 m2g−1; to ...our knowledge, currently the highest published for Zr‐based MOFs. CH4/CO2/H2 adsorption isotherms were obtained over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions. The total hydrogen adsorption at 65 bar and 77 K is 0.092 g g−1, which corresponds to 43 g L−1. The volumetric and gravimetric methane‐storage capacities at 65 bar and 298 K are approximately 180 vSTP/v and 0.27 g g−1, respectively.
Natural‐gas vehicle: A new Zr‐based metal–organic framework material, NU‐1100, with a pore volume of 1.53 ccg−1 and Brunauer–Emmett–Teller (BET) surface area of 4020 m2g−1 was designed, synthesized, and characterized. CH4/CO2/H2 adsorption isotherms were obtained over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions (see figure).
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The physical limits for methane storage and delivery in nanoporous materials were investigated, with a focus on whether it is possible to reach a methane deliverable capacity of 315 cm3(STP)/cm3 in ...line with the adsorption target established by the ARPA-E agency. Our efforts focused on how both geometric and chemical properties, such as void fraction (V f), volumetric surface area (S v), and heat of adsorption (Q st), impact methane deliverable capacity, i.e., the amount of methane adsorbed at some storage pressure minus the amount adsorbed at the delivery pressure. With the aid of grand canonical Monte Carlo (GCMC) simulations, we studied methane adsorption and delivery properties in a population of 122 835 hypothetical pcu metal–organic frameworks (MOFs) and 39 idealized carbon-based porous materials. From the simulation results, we developed an analytical equation that helped us delimit the necessary material properties to reach specific methane deliverable capacity targets. The maximum deliverable capacity between 65 and 5.8 bar among the hypothetical MOFs was 206 cm3(STP)/cm3 at 298 K. We found that artificially increasing the methane–MOF interaction strength by increasing the Lennard-Jones ε parameters of the MOF atoms by 2- and 4-fold only improved the maximum deliverable capacity up to 223 and 228 cm3(STP)/cm3, respectively. However, the effect on the amount stored at 65 bar was more significant, which suggested another strategy; raising the temperature of the system by 100 K can recover ∼70% of the methane stranded at the delivery pressure. By increasing the delivery temperature to 398 K, the ARPA-E target was reached by a few hypothetical MOFs with quadrupled ε values. This work shows the difficulty in reaching the ARPA-E target but also suggests that a strategy that combines a material with a large volumetric density of sites that interact strongly with methane and raising the delivery temperature can greatly improve the performance of nanoporous materials for methane storage and delivery. The optimal heat of adsorption in an isothermal storage and delivery scenario is approximately 10.5–14.5 kJ/mol, whereas in the nonisothermal storage and delivery scenario the optimal heats of adsorption fell within a range of 11.8–19.8 kJ/mol.
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We show that the MOF NU-111 exhibits equally high volumetric and gravimetric methane uptake values, both within ≈75% of the DOE targets at 300 K. Upon reducing the temperature to 270 K, the uptake ...increases to 0.5 g g(-1) and 284 cc(STP) per cc at 65 bar. Adsorption of CO2 and H2 is also reported. Simulated isotherms are in excellent agreement with those obtained from experiments.
We have successfully used a highly efficient copper-catalyzed “click” reaction for the synthesis of a new series of hexacarboxylic acid linkers with varying sizes for the construction of isoreticular ...(3,24)-connected metal–organic frameworks (MOFs)namely, NU-138, NU-139, and NU-140. One of these MOFs, NU-140, exhibits a gravimetric methane uptake of 0.34 g/g at 65 bar and 298 K, corresponding to almost 70% of the DOE target (0.5 g/g), and has a working capacity (deliverable amount between 65 and 5 bar) of 0.29 g/g, which translates into a volumetric working capacity of 170 cc(STP)/cc. These values demonstrate that NU-140 performs well for methane storage purposes, from both a gravimetric and a volumetric point of view. Adsorption of CO2 and H2 along with simulated isotherms are also reported.
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Correction for 'Atomic layer deposition of Cu(
i
) oxide films using Cu(
ii
) bis(dimethylamino-2-propoxide) and water' by J. R. Avila,
et al.
,
Dalton Trans.
, 2017, DOI:
10.1039/c6dt02572b
.
Discovery of new adsorbent materials with a high CO2 working capacity could help reduce CO2 emissions from newly commissioned power plants using precombustion carbon capture. High-throughput ...computational screening efforts can accelerate the discovery of new adsorbents but sometimes require significant computational resources to explore the large space of possible materials. We report the in silico discovery of high-performing adsorbents for precombustion CO2 capture by applying a genetic algorithm to efficiently search a large database of metal-organic frameworks (MOFs) for top candidates. High-performing MOFs identified from the in silico search were synthesized and activated and show a high CO2 working capacity and a high CO2/H2 selectivity. One of the synthesized MOFs shows a higher CO2 working capacity than any MOF reported in the literature under the operating conditions investigated here.
Improvement of light harvesting in semiconductor quantum dots (QDs) is essential for the development of efficient QD-based solar energy conversion systems. In this study, plasmon-enhanced light ...absorption in CdSe QDs sensitized on silver (Ag) nanoparticle (NP) films was examined as a function of interparticle (QD to Ag NP) distance. Up to 24-fold plasmonic enhancement of fluorescence from QDs was observed when the particle separation distance was ≥5 nm. The enhancement effect was observed to largely sustain the exciton lifetimes in QDs and to strongly depend on the incident photon wavelength following the plasmon resonant strength of Ag NPs, confirming that the enhanced photoluminescence was mainly due to the enhancement in photoabsorption in CdSe QDs by the plasmon of Ag NPs. This study suggests applications of Ag NPs in QD-based solar energy conversion for significantly improving light harvesting in QDs.
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The synthesis of a porous organic polymer (POP) containing free-base porphyrin subunits has been accomplished by the condensation of a bis(phthalic acid)porphyrin with tetra(4-aminophenyl)methane. ...Metallation by post-synthesis modification affords microporous materials incorporating either Fe or Mn(porphyrins) that have been shown to be active catalysts for both olefin epoxidation and alkane hydroxylation.
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