Further investigation of the effect of framework catenation on hydrogen uptake in metal-organic frameworks

Hydrogen-sorption studies have been carried out for the catenation isomer pairs of PCN-6 and PCN-6' (both have the formula of Cu(3)(TATB)(2), where TATB represents 4,4',4'-s-triazine-2,4,6-triyl-tribenzoate with a formula of C(24)H(12)N(3)O(6)). Inelastic neutron scattering (INS) studies reveal that the initial sites occupied by adsorbed H(2) are the open Cu centers of the paddlewheel units with comparable interaction energies in the two isomers. At high H(2) loadings, where the H(2) molecules adsorb mainly on or around the organic linkers, the interaction is found to be substantially stronger in catenated PCN-6 than in noncatenated PCN-6', leading to much higher H(2) uptake in the isomer with catenation. Hydrogen sorption measurements at pressures up to 50 bar demonstrate that framework catenation can be favorable for the enhancement of hydrogen adsorption. For example, the excess hydrogen uptake of PCN-6 is 72 mg/g (6.7 wt %) at 77 K/50 bar or 9.3 mg/g (0.92 wt %) at 298 K/50 bar, respectively, and that for PCN-6' is 42 mg/g (4.0 wt %) at 77 K/50 bar or 4.0 mg/g (0.40 wt %) at 298 K/50 bar. Importantly, PCN-6 exhibits a total hydrogen uptake of 95 mg/g (8.7 wt %) (corresponding to a total volumetric value of 53.0 g/L, estimated based on crystallographic density) at 77 K/50 bar and 15 mg/g (1.5 wt %) at 298 K/50 bar. Significantly, the expected usable capacity of PCN-6 is as high as 75 mg/g (or 41.9 g/L) at 77 K, if a recharging pressure of 1.5 bar is assumed.     

High-capacity hydrogen and nitric oxide adsorption and storage in a metal-organic framework

Gas adsorption experiments have been carried out on a copper benzene tricarboxylate metal-organic framework material, HKUST-1. Hydrogen adsorption at 1 and 10 bar (both 77 K) gives an adsorption capacity of 11.16 mmol H2 per g of HKUST-1 (22.7 mg g(-)1, 2.27 wt %) at 1 bar and 18 mmol per g (36.28 mg g(-)1, 3.6 wt %) at 10 bar. Adsorption of D2 at 1 bar (77 K) is between 1.09 (at 1 bar) and 1.20(at <100 mbar) times the H2 values depending on the pressure, agreeing with the theoretical expectations. Gravimetric adsorption measurements of NO on HKUST-1 at 196 K (1 bar) gives a large adsorption capacity of approximately 9 mmol g(-1), which is significantly greater than any other adsorption capacity reported on a porous solid. At 298 K the adsorption capacity at 1 bar is just over 3 mmol g(-1). Infra red experiments show that the NO binds to the empty copper metal sites in HKUST-1. Chemiluminescence and platelet aggregometry experiments indicate that the amount of NO recovered on exposure of the resulting complex to water is enough to be biologically active, completely inhibiting platelet aggregation in platelet rich plasma.     

Covalent organic frameworks as exceptional hydrogen storage materials

We report the H2 uptake properties of six covalent organic frameworks (COFs) from first-principles-based grand canonical Monte-Carlo simulations. The predicted H2 adsorption isotherm is in excellent agreement with the only available experimental result (3.3 vs 3.4 wt % at 50 bar and 77 K for COF-5), also reported here, validating the predictions. We predict that COF-105 and COF-108 lead to a reversible excess H2 uptake of 10.0 wt % at 77 K, making them the best known storage materials for molecular hydrogen at 77 K. We predict that the total H2 uptake for COF-108 is 18.9 wt % at 77 K. COF-102 shows the best volumetric performance, storing 40.4 g/L of H2 at 77 K. These results indicate that the COF systems are most promising candidates for practical hydrogen storage.     

Microporous Polymers from a Carbazole‐Based Triptycene Monomer: Synthesis and Their Applications for Gas Uptake

Two kinds of novel organic microporous polymers TCP s ( TCP‐A and TCP‐B ) were prepared by two cost‐effective synthetic strategies from the monomer of tricarbazolyltriptycene ( TCT ). Their structure and properties were characterized by FT‐IR, solid ¹³C NMR, powder XRD, SEM, TEM, and gas absorption measurements. TCP‐B displayed a high surface area (1469 m² g^?1) and excellent H₂ storage (1.70 wt % at 1 bar/77 K) and CO₂ uptake abilities (16.1 wt % at 1 bar/273 K), which makes it a promising material for potential application in gas storage.     

Metal Microporous Aromatic Polymers with Improved Performance for Small Gas Storage

A novel metal‐doping strategy was developed for the construction of iron‐decorated microporous aromatic polymers with high small‐gas‐uptake capacities. Cost‐effective ferrocene‐functionalized microporous aromatic polymers (FMAPs) were constructed by a one‐step Friedel–Crafts reaction of ferrocene and s‐triazine monomers. The introduction of ferrocene endows the microporous polymers with a regular and homogenous dispersion of iron, which avoids the slow reunion that is usually encountered in previously reported metal‐doping procedures, permitting a strong interaction between the porous solid and guest gases. Compared to ferrocene‐free analogues, FMAP‐1, which has a moderate BET surface area, shows good gas‐adsorption capabilities for H₂ (1.75 wt % at 77 K/1.0 bar), CH₄ (5.5 wt % at 298 K/25.0 bar), and CO₂ (16.9 wt % at 273 K/1.0 bar), as well as a remarkably high ideal adsorbed solution theory CO₂/N₂ selectivity (107 v/v at 273 K/(0–1.0) bar), and high isosteric heats of adsorption of H₂ (16.9 kJ mol^?1) and CO₂ (41.6 kJ mol^?1).     

A ferrocene‐containing porous organic polymer linked by tetrahedral silicon‐centered units for gas sorption

A novel ferrocene‐containing porous organic polymer (FPOP) has been prepared by Sonogashira‐Hagihara coupling reaction of 1,1′‐dibromoferrocene and tetrakis(4‐ethynylphenyl)silane. Compared with other polymers, the resulting polymer possesses excellent thermal stability with the decomposition temperature of 415°C and high porosity with Brunauer–Emmett–Teller (BET) surface area of 542 m² g^?1 as measured by nitrogen adsorption‐desoprtion isotherm at 77 K. For applications, it shows moderate carbon dioxide uptakes of up to 1.42 mmol g^?1 (6.26 wt%) at 273 K/1.0 bar and 0.82 mmol g^?1 (3.62 wt%) at 298 K/1.0 bar, and hydrogen capacity of up to 0.45 mmol g^?1 (0.91 wt%) at 77 K/1.0 bar, indicating that FPOP might be utilized as a promising candidate for storing carbon dioxide and hydrogen. Although FPOP possesses lower porosity than many porous polymers, the gas capacities are higher or comparable to them, thereby revealing that the incorporation of ferrocene units into the network is an effective strategy to enhance the affinity between the framework and gas.     

A Triptycene-Based Porous Organic Polymer that Exhibited High Hydrogen and Carbon Dioxide Storage Capacities and Excellent CO2/N2 Selectivity

A novel porous organic polymer (POP) has been constructed through the condensation of triptycene tricatechol and 1,3,5‐benzenetris(4‐phenylboronic acid). This triptycene‐based POP exhibited high H₂ uptake (up to 1.84 wt% at 77 K, 1 bar), large CO₂ adsorption capacity (up to 18.1 wt% at 273K, 1 bar), and excellent CO₂/N₂ adsorption selectivity (up to 120/1). The influence of solvent on the gas adsorption performance of the POP has also been investigated.     

Hydrogen adsorption in an interpenetrated dynamic metal-organic framework

A metal-organic framework Zn(NDC)(4,4'-Bpe)(0.5).xG [NDC = 2,6-naphthalenedicarboxylate; 4,4'-Bpe = 4,4'-trans-bis(4-pyridyl)ethylene; G = guest molecules] has been synthesized, structurally characterized, and rationalized to be a two-interpenetrated elongated primitive cubic net. Powder X-ray diffraction and adsorption studies reveal the dynamic feature of the framework, which can take up hydrogen of about 2.0 wt % at 77 K and 40 bar and 0.3 wt % at 298 K and 65 bar.     

Novel (3,4,6)-connected metal-organic framework with high stability and gas-uptake capability

A microporous and noninterpenetrated metal-organic framework [Cu(3)(L)(2)(DABCO)(H(2)O)]·15H(2)O·9DMF (1) has been synthesized using two different ligands, [1,1':3',1″-terphenyl]-4,4″,5'-tricarboxylic acid (H(3)L) and 1,4-diazabicyclo[2.2.2]octane (DABCO). As revealed by variable-temperature powder X-ray diffraction (VT-PXRD) measurements, N,N'-ditopic DABCO plays an important role for stabilization of the Cu-L framework. The three-dimensional framework of 1 exhibits high stability and excellent adsorption capacity for H(2) (54.3 mg g(-1) at 77 K and 20 bar), CO(2) (871 mg g(-1) at 298 K and 20 bar), CH(4) (116.7 mg g(-1), 99 cm(3) (STP) cm(-3) at 298 K and 20 bar), and n-pentane (686 mg g(-1) at 298 K and 1 bar). Interestingly, the excellent selectivity toward CO(2) over N(2) at ambient temperature (273 and 298 K) and 1 bar makes complex 1 possess practical application in gas separation and purification.     

Tetra-armed conjugated microporous polymers for gas adsorption and photocatalytic hydrogen evolution

Two novel tetra-armed conjugated microporous polymers with different geometries have been designed and synthesized via Suzuki-Miyaura cross coupling polycondensation. Both polymers are stable in various organic solvents tested and are thermally stable. The pyrene-containing polymer of PrPy with the rigid pyrene unit shows a higher Brunauer-Emmet-Teller specific surface area of 1219 m~2 g~(-1) than the tetraphenylethylene-containing polymer of PrTPE(770 m~2 g~(-1)), which leads to a high CO_2 uptake ability of 3.89 mmol g~(-1) at 1.13 bar/273 K and a H_2 uptake ability of 1.69 wt% at 1.13 bar/77 K. The photocatalytic hydrogen production experiments revealed that PrPy also shows a better photocatalytic performance than PrTPE due to the higher conjugation degree and planar structure, the broader UV-visible(UV-Vis) absorption, the lower photoluminescence lifetime, and the higher specific surface area.     

A mesoporous metal-organic framework constructed from a nanosized C3-symmetric linker and [Cu24(isophthalate)24] cuboctahedra

The mesoporous framework [Cu(3)(L)(H(2)O)(3)]·(DMF)(35)·(H(2)O)(35) (NOTT-119) shows on desolvation a BET surface area of 4118(200) m(2) g(-1), a pore volume of 2.35 cm(3) g(-1), a total H(2) uptake of 101 mg g(-1) at 60 bar, 77 K and a total CH(4) uptake of 327 mg g(-1) at 80 bar, 298 K.     

Influence of MgO template on carbon dioxide adsorption of cation exchange resin-based nanoporous carbon

In this work, porous carbons with well-developed pore structures were directly prepared from a weak acid cation exchange resin (CER) by the carbonization of a mixture with Mg acetate in different ratios. The effect of the Mg acetate-to-CER ratio on the pore structure and CO(2) adsorption capacities of the obtained porous carbons was studied. The textural properties and morphologies of the porous carbons were analyzed via N(2)/77K adsorption/desorption isotherms, SEM, and TEM, respectively. The CO(2) adsorption capacities of the prepared porous carbons were measured at 298 K and 1 bar and 30 bar. By dissolving the MgO template, the porous carbons exhibited high specific surface areas (326-1276 m(2)/g) and high pore volumes (0.258-0.687 cm(3)/g). The CO(2) adsorption capacities of the porous carbons were enhanced to 164.4 mg/g at 1 bar and 1045 mg/g at 30 bar by increasing the Mg acetate-to-CER ratio. This result indicates that CER was one of the carbon precursors to producing the porous structure, as well as for improving the CO(2) adsorption capacities of the carbon species.     

Isostructural Metal–Organic Frameworks Assembled from Functionalized Diisophthalate Ligands through a Ligand‐Truncation Strategy

Four isostructural metal–organic frameworks (MOFs) with various functionalized pore surfaces were synthesized from a series of diisophthalate ligands. These MOFs exhibit a new network topology of {4.6⁴.8}₂{4².6⁴}{6⁴.8²}₂{6⁶}. Hydrogen uptake as high as 2.67 wt % at 77 K/1 bar and CO₂ uptake of 15.4 wt % at 297 K/1 bar have been observed for PCN‐308, which contains ? CF₃ groups. The isostructural series of MOFs also showed reasonable adsorption selectivity of CO₂ over CH₄ and N₂.     

The potential of organic polymer-based hydrogen storage materials

The challenge of storing hydrogen at high volumetric and gravimetric density for automotive applications has prompted investigations into the potential of cryo-adsorption on the internal surface area of microporous organic polymers. A range of Polymers of Intrinsic Microporosity (PIMs) has been studied, the best PIM to date (a network-PIM incorporating a triptycene subunit) taking up 2.7% H(2) by mass at 10 bar/77 K. HyperCrosslinked Polymers (HCPs) also show promising performance as H(2) storage materials, particularly at pressures >10 bar. The N(2) and H(2) adsorption behaviour at 77 K of six PIMs and a HCP are compared. Surface areas based on Langmuir plots of H(2) adsorption at high pressure are shown to provide a useful guide to hydrogen capacity, but Langmuir plots based on low pressure data underestimate the potential H(2) uptake. The micropore distribution influences the form of the H(2) isotherm, a higher concentration of ultramicropores (pore size <0.7 nm) being associated with enhanced low pressure adsorption.     

Metal-organic framework from an anthracene derivative containing nanoscopic cages exhibiting high methane uptake

A microporous metal-organic framework, PCN-14, based on an anthracene derivative, 5,5'-(9,10-anthracenediyl)di-isophthalate (H4adip), was synthesized under solvothermal reaction conditions. X-ray single crystal analysis revealed that PCN-14 consists of nanoscopic cages suitable for gas storage. N2-adsorption studies of PCN-14 at 77 K reveal a Langmuir surface area of 2176 m2/g and a pore volume of 0.87 cm3/g. Methane adsorption studies at 290 K and 35 bar show that PCN-14 exhibits an absolute methane-adsorption capacity of 230 v/v, 28% higher than the DOE target (180 v/v) for methane storage.     

A robust porous metal-organic framework with a new topology that demonstrates pronounced porosity and high-efficiency sorption/selectivity properties of small molecules

A robust porous metal-organic framework (MOF), [Co(3)(ndc)(HCOO)(3)(μ(3)-OH)(H(2)O)](n) (1) (H(2)ndc=5-(4-pyridyl)-isophthalic acid), was synthesized with pronounced porosity. MOF 1 contained two different types of nanotubular channels, which exhibited a new topology with the Schlafli symbol of {4(2).6(5).8(3)}{4(2).6}. MOF 1 showed high-efficiency for the selective sorption of small molecules, including the energy-correlated gases of H(2), CH(4), and CO(2), and environment-correlated steams of alcohols, acetone, and pyridine. Gas-sorption experiments indicated that MOF 1 exhibited not only a high CO(2)-uptake (25.1 wt % at 273 K/1 bar) but also the impressive selective sorption of CO(2) over N(2) and CH(4). High H(2)-uptake (2.04 wt % at 77 K/1 bar) was also observed. Moreover, systematic studies on the sorption of steams of organic molecules displayed excellent capacity for the sorption of the homologous series of alcohols (C(1)-C(5)), acetone, pyridine, as well as water.     

Hydrogen adsorption in microporous hypercrosslinked polymers

A microporous hypercrosslinked polymer resin was synthesized and shown to adsorb 3.04 wt.% hydrogen at 77 K and 15 bar; this represents the highest level of hydrogen adsorption yet observed for an organic polymer.     

New multifunctional porous materials based on inorganic-organic hybrid single-walled carbon nanotubes: gas storage and high-sensitive detection of pesticides

Single-walled carbon nanotubes (SWNTs) that are covalently functionalized with benzoic acid (SWNT-PhCOOH) can be integrated with transition-metal ions to form 3D porous inorganic-organic hybrid frameworks (SWNT-Zn). In particular, N(2) -adsorption analysis shows that the BET surface area increases notably from 645.3 to 1209.9?m(2) g(-1) for SWNTs and SWNT-Zn, respectively. This remarkable enhancement in the surface area of SWNT-Zn is presumably due to the microporous motifs from benzoates coordinated to intercalated zinc ions between the functionalized SWNTs; this assignment was also corroborated by NLDFT pore-size distributions. In addition, the excess-H(2) -uptake maximum of SWNT-Zn reaches about 3.1?wt.?% (12?bar, 77?K), which is almost three times that of the original SWNTs (1.2?wt.?% at 12?bar, 77?K). Owing to its inherent conductivity and pore structure, as well as good dispersibility, SWNT-Zn is an effective candidate as a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs): By using solid-phase extraction (SPE) with SWNT-Zn-modified glassy carbon electrode, the detection limit of methyl parathion (MP) is 2.3?ng?mL(-1) .     

Fluorinated Porous Poly(spirobifluorene) Via Direct C‒H Arylation: Characterization,Porosity, and Gas Uptake

Considering intrinsic properties of conjugated polyfluorenes and special functions of porous polymers, synthesis of fluorinated porous poly(spirobifluorene) via direct C?H arylation polycondensation is explored. Owing to the contorted structure and cross-linking nature, the obtained polymer FPSBF shows permanent porosities with Brunauer–Emmett–Teller specific surface area up to 700 m² g^?1 and exhibits a narrow pore size distribution with the dominant pore size at about 0.63 nm, which is more suitable for adsorption of small gas molecules. Based on the measured gas physisorption isotherms with pressure up to 1.13 bar, the obtained polymer shows good uptaking capacities for hydrogen (1.30 wt% at 1.0 bar and 77 K) and methane (4.80 wt% 1.0 bar and 273 K). Moreover, FPSBF has significant adsorption selectivity for CH₄ against N₂ and the estimated ideal adsorption selectivity ratio is up to 30/1 at 1.0 bar and 273 K, which makes the material possess potential application in gas separation.     

High gas sorption and metal-ion exchange of microporous metal-organic frameworks with incorporated imide groups

Metal-organic frameworks (MOFs), {[Cu(2)(bdcppi)(dmf)(2)]·10DMF·2H(2)O}(n) (SNU-50) and {[Zn(2)(bdcppi)(dmf)(3)]·6DMF·4H(2)O}(n) (SNU-51), have been prepared by the solvothermal reactions of N,N'-bis(3,5-dicarboxyphenyl)pyromellitic diimide (H(4)BDCPPI) with Cu(NO(3))(2) and Zn(NO(3))(2), respectively. Framework SNU-50 has an NbO-type net structure, whereas SNU-51 has a PtS-type net structure. Desolvated solid [Cu(2)(bdcppi)](n) (SNU-50'), which was prepared by guest exchange of SNU-50 with acetone followed by evacuation at 170 °C, adsorbs high amounts of N(2), H(2), O(2), CO(2), and CH(4) gases due to the presence of a vacant coordination site at every metal ion, and to the presence of imide groups in the ligand. The Langmuir surface area is 2450 m(2) g(-1). It adsorbs H(2) gas up to 2.10 wt% at 1 atm and 77 K, with zero coverage isosteric heat of 7.1 kJ mol(-1), up to a total of 7.85 wt% at 77 K and 60 bar. Its CO(2) and CH(4) adsorption capacities at 298 K are 77 wt% at 55 bar and 17 wt% at 60 bar, respectively. Of particular note is the O(2) adsorption capacity of SNU-50' (118 wt% at 77 K and 0.2 atm), which is the highest reported so far for any MOF. By metal-ion exchange of SNU-51 with Cu(II), {[Cu(2)(bdcppi)(dmf)(3)]·7DMF·5H(2)O}(n) (SNU-51-Cu(DMF)) with a PtS-type net was prepared, which could not be synthesized by a direct solvothermal reaction.