Guest driven rearrangements of protonation and hydrogen bonding in decavanadate anions as their tetraalkylammonium salts

Single crystal X-ray structure determinations of [(n-C5H11)4N]3[H3V10O28].2(CH3)2CO (TAA-acetone), [(n-C5H11)4N]8[H3V10O28]2[H4V10O28].7C4H8O2 (TAA-dioxane), [(n-C5H11)4N]3[H3V10O28] (TAAh) and [(n-C6H13)4N]2[H4V10O28].4C4H8O2 (THA-dioxane) revealed that protonation and hydrogen bond formation of decavanadate anions in their tetraalkylammonium salts are influenced by the nature of the solvent molecules incorporated as guests into the crystals. When crystallized with acetone molecules, the decavanadate anion forms a self-associated hydrogen-bonded dimer of ([H3V10O28](3-))2 to hide the protons from the aprotic protophobic acetone molecules. When crystallized with 1,4-dioxane molecules, the decavanadate anion exposes its protons to the aprotic protophilic 1,4-dioxane molecules to form a hydrogen-bond assisted solvation complex of ((C4H8O2)4...[H4V10O28)](2-)). Size effects of the tetraalkylammonium cations on crystallizing these hydrogen-bonded assemblies were also examined.     

A porous framework polymer based on a zinc(II) 4,4'-bipyridine-2,6,2',6'-tetracarboxylate: synthesis, structure, and "zeolite-like" behaviors

The robust metal-organic framework compound {[Zn(2)(L)] x 4H(2)O}(infinity) I has been synthesized by hydrothermal reaction of ZnCl(2) and 4,4'-bipyridine-2,6,2',6'-tetracarboxylic acid (H(4)L). Compound I crystallizes in a chiral space group, P4(2)2(1)2, with the chirality generated by the helical chains of hydrogen-bonded guest water molecules rather than by the coordination framework. Removal of guest water molecules from the crystal affords the porous material, [Zn(2)(L)](infinity) (II), which has very high thermal stability and is chemically inert. The N(2) isotherm of II at 77 K suggests a uniform porous structure with a BET surface area of 312.7 m(2)/g and a remarkably strong interaction with N(2) molecules (betaE(0) = 29.6 kJ mol(-)(1)). II also exhibits significant gas storage capacities of 1.08 wt % for H(2) at 4 bar and 77 K and 3.14 wt % (44.0 cm(3)/g, 67 v/v) for methane at 9 Bar at 298 K. The adsorption behavior of II toward organic solvent vapors has also been studied, and isotherms reveal that for different solvent vapors adsorption is dominated by two types of processes, absorbate-absorbate or absorbate-absorbent interactions. The adsorption and desorption kinetic processes in II are determined mainly by the molecular size of the guest species and their interaction with the host.     

Hydrogen adsorption in a highly stable porous rare-earth metal-organic framework: sorption properties and neutron diffraction studies

A highly stable porous lanthanide metal-organic framework, Y(BTC)(H2O).4.3H2O (BTC = 1,3,5-benzenetricarboxylate), with pore size of 5.8 A has been constructed and investigated for hydrogen storage. Gas sorption measurements show that this porous MOF exhibits highly selective sorption behaviors of hydrogen over nitrogen gas molecules and can take up hydrogen of about 2.1 wt % at 77 K and 10 bar. Difference Fourier analysis of neutron powder diffraction data revealed four distinct D2 sites that are progressively filled within the nanoporous framework. Interestingly, the strongest adsorption sites identified are associated with the aromatic organic linkers rather than the open metal sites, as occurred in previously reported MOFs. Our results provide for the first time direct structural evidence demonstrating that optimal pore size (around 6 A, twice the kinetic diameter of hydrogen) strengthens the interactions between H2 molecules and pore walls and increases the heat of adsorption, which thus allows for enhancing hydrogen adsorption from the interaction between hydrogen molecules with the pore walls rather than with the normally stronger adsorption sites (the open metal sites) within the framework. At high concentration H2 loadings (5.5 H2 molecules (3.7 wt %) per Y(BTC) formula), H2 molecules form highly symmetric novel nanoclusters with relatively short H2-H2 distances compared to solid H2. These observations are important and hold the key to optimizing this new class of rare metal-organic framework (RMOF) materials for practical hydrogen storage applications.     

Borromean-entanglement-driven assembly of porous molecular architectures with anion-modified pore space

A series of metal-organic frameworks based on a flexible, highly charged Bpybc ligand, namely 1?Mn?OH(-), 2?Mn?SO(4)(2-), 3?Mn?bdc(2-), 4?Eu?SO(4)(2-) (H(2)BpybcCl(2) = 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride, H(2)bdc = 1,4-benzenedicarboxylic acid) have been obtained by a self-assembly process. Single-crystal X-ray-diffraction analysis revealed that all of these compounds contained the same n-fold 2D→3D Borromean-entangled topology with irregular butterfly-like pore channels that were parallel to the Borromean sheets. These structures were highly tolerant towards various metal ions (from divalent transition metals to trivalent lanthanide ions) and anion species (from small inorganic anions to bulky organic anions), which demonstrated the superstability of these Borromean linkages. This non-interpenetrated entanglement represents a new way of increasing the stability of the porous frameworks. The introduction of bipyridinium molecules into the porous frameworks led to the formation of cationic surface, which showed high affinities to methanol and water vapor. The distinct adsorption and desorption isotherms of methanol vapor in four complexes revealed that the accommodated anion species (of different size, shape, and location) provided a unique platform to tune the environment of the pore space. Measurements of the adsorption of various organic vapors onto framework 1?Mn?OH(-) further revealed that these pores have a high adsorption selectivity towards molecules with different sizes, polarities, or π-conjugated structures.     

Effects of pore structure and surface chemical characteristics on the adsorption of organic vapors on titanate nanotubes

Effects of pore structure and surface chemical characteristics of titanate nanotubes (TNTs) on their adsorptive removal of organic vapors were investigated. TNTs were prepared via a hydrothermal treatment of TiO₂ powders in a 10 M NaOH solution at 150?°C for 24?h, and subsequently washed with HCl aqueous solution of different concentrations. Effects of acid washing process (or the sodium content) on the microstructures and surface chemical characteristics of TNTs were characterized with nitrogen adsorption-desorption isotherms, FTIR, and water vapor adsorption isotherms. For the adsorption experiments, gravimetric techniques were employed to determine the adsorption capacities of TNTs for four organic vapors with similar heats of vaporization (i.e., comparable heats of adsorption) but varying dipole moments and structures, including n-hexane, cyclohexane, toluene, and methyl ethyl ketone (MEK), at isothermal conditions of 20 and 25?°C. The experimental data were correlated by well-known vapor phase models including BET and GAB models. Isosteric heats of adsorption were calculated and heat curves were established. Equilibrium isotherms of organic vapors on TNTs were type II, characterizing vapor condensation to form multilayers. The specific surface area (and pore volume) and hydrophilicity of TNTs were the dominating factors for the determination of their organic vapors adsorption capacity. The GAB isotherm equation fitted the experimental data more closely than the BET equation. The heats of adsorption showed that the adsorption of organic vapors on TNTs was primarily due to physical forces and adsorbates with larger polarity might induce a stronger interaction with TNTs.     

Exceptional framework flexibility and sorption behavior of a multifunctional porous cuprous triazolate framework

The porous metal azolate framework [Cu(etz)]infinity (MAF-2, Hetz = 3,5-diethyl-1,2,4-triazole) processes an NbO type cuprous triazolate scaffold and a CsCl type hydrophobic channel system, in which the large cavities are interconnected by small apertures with pendant ethyl groups. Since the ethyl-blocked apertures behave as thermoactivated IRIS stops for the guest molecules, the gas sorption behavior of MAF-2 can be controlled by temperature, in which N2 adsorption was observed at 195 K rather than 77 K. Single-crystal X-ray structural analysis revealed that the [Cu(etz)]infinity host framework is not altered upon N2 inclusion, confirming the occurrence of the so-called " kinetically controlled flexibility". By virtue of the kinetically controlled flexibility and hydrophobic pore surface, MAF-2 can adsorb large amounts of small organic molecules but excludes H2O. As demonstrated by single-crystal X-ray structural analyses, MAF-2 shrinks, expands, or distorts its framework to accommodate the hydrogen-bonded hexamers of MeOH, EtOH, or MeCN, respectively. Moreover, MAF-2 can also separate benzene and cyclohexane efficiently, as its flexible scaffold can distort to a certain degree so that benzene can diffuse through the distorted apertures but cyclohexane cannot. Moreover, the adsorption/desorption of these organic vapors induces reversible, multimode structural transformations.     

Mesopore control of high surface area NaOH-activated carbon

Activated carbon with BET surface areas in a narrow range from 2318 to 2474 m2/g was made by soaking the char made from corncob in a concentrated NaOH solution at NaOH/char ratios from 3 to 6; the mesopore volumes of the activated carbon were significantly changed from 21 to 58%. The relationships between pore properties (Sp, Vpore, Vmicro/Vpore, Dp) and NaOH dosage were investigated. Comparisons between the methods of NaOH and KOH activation revealed that NaOH activation can suitably control the mesopore specific volume of the activated carbon. Elemental analysis revealed that the H/C and O/C values of the activated carbons of NaOH/char ratios from 3 to 6 were significantly lower. SEM observation of surface hole variation of the activated carbon ascertained that the reaction process was inner pore etching. Based on the above three measurements and experimental investigations, the assumption made by previous researchers, namely that NaOH and KOH produce similar results, was challenged. Furthermore, the adsorption kinetics was used to investigate the adsorption rate of an Elovich equation to determine the relationships between the adsorption behavior on larger molecules (dyes) and smaller molecules (phenols) and the pore structure of the activated carbon.     

Adsorption behavior of surface-chemically pure N-alkyl-N-(2-hydroxyethyl)aldonamides at the air/water interface

N-alkyl-N-(2-hydroxyethyl)aldonamides (alkyl: n-C6H13, n-C8H17, n-C10H21, n-C12H25, and n-C14H29) were obtained in the reaction of long-chain N-alkyl-N-(2-hydroxyethyl)amines with D-glucono-1,5-lactone and D-glucoheptono-1,4-lactone. The adsorption isotherms were obtained from surface tension measurements of aqueous solutions of surface-chemically pure surfactants. The experimental equilibrium surface tension versus concentration isotherms were evaluated by the Frumkin adsorption equation to get the adsorption parameters, namely, standard free energy of adsorption, deltaG(o)ad, saturation adsorption, gammainfinity minimum surface area demand per molecule adsorbed, Amin, and interaction parameter, Hs. The investigated functionalized alkylaldonamides show improved solubility in comparison with the corresponding sugar derivatives of the primary amines. The introduction of the -CHOH moiety into the saccharide headgroup causes a noticeable increase of the hydrophobic character of surfactant. The minimum surface area demand, Amin, is slightly greater for glucoheptonamides than for the corresponding gluconamides. The practically constant Amin value within the homologue series of the aldonamides indicates that the obtuse hydroxyethyl residue is the determining factor for the arrangement of the adsorbed surfactants in the interfacial layer.     

有机膦、胂、(月弟)合钨、钼聚多酸盐的研究 Ⅳ.烷基膦合钼聚多酸盐的制备

本文是作者在合成了一系列有机胂、有机(月弟)的钨、钼聚多酸盐后,有关若干有机膦合钼聚多酸“柄状”化合物的合成报导以及一些光学性质的测定。有关有机基团是C_2H_5,n-C_3H_7,n-C_4H_9,n-C_5H_(11)及C_6H_5CH_2。发现pH为3～5时,在不同的投料比例下都只形成一种类型的化合物[(RP)_2Mo_5O_(21)]~(4-),与相应的有机胂衍生物既可形成[(RAs)_2Mo_5O_(21)]~(4-)又可形成[(RAs)_2Mo_6O_(24)]~(4-)有较大的差异。     

Adsorption of a diverse set of organic vapors on quartz, CaCO3, and alpha-Al2O3 at different relative humidities

Adsorption constants of a diverse set of 50 organic vapors have been measured on quartz (SiO(2)), CaCO(3), and alpha-Al(2)O(3) at different relative humidities at 15 degrees C. For nonpolar compounds we found an exponential decrease of the adsorption constants on a given mineral between 40 and 97% relative humidity. Extrapolated to 100% relative humidity, the adsorption constants of nonpolar compounds on the different minerals coincide and agree with those measured on a bulk water surface. The adsorption constants of polar compounds also decrease with increasing humidity up to 90%, but between 90% and 100% they increase again. We speculate that this effect is due to a change in the orientation of the water molecules that form the surface at which the organic vapors adsorb at this high humidity. The compound variability in the adsorption constants of all compounds on a given surface at a given relative humidity could be described rather well with a linear free energy relationship using Abraham's solvation parameters for the van der Waals and electron-donor/acceptor properties of the compounds. The remaining deviation between fitted and experimental data was found to be systematic, which indicated that an optimized parameter set for the used compounds could still considerably improve the fit.     

Benzene-templated hydrothermal synthesis of metal-organic frameworks with selective sorption properties

In this paper, we report two metal-organic frameworks [Co3(ndc)3(bipyen)(1.5)]H2O (1) and [Co2(ndc)2bipyen)]C6H6.H2O (2) (bipyen=trans-1,2-bis(4-pyridyl)ethylene, H2ndc=2,6-naphthalenedicarboxylic acid). These compounds were both synthesized from identical hydrothermal reaction conditions except that benzene was added to the reaction for 2. Crystal structures show that the two compounds have triply interpenetrated three-dimensional frameworks and these frameworks have the same primary structure of a two-dimensional network of interconnected [Co2(O2CR)(4/2)] (R=naphthalene group) paddle-wheels and bridging bipyen ligands. Both compounds have guest water molecules and, in addition, 2 has guest benzene molecules. Structural transformations of the host accompanied guest removal, which can be monitored by powder X-ray diffraction. N2 adsorption data of 2 show that there are two different types of pores corresponding to the benzene and water pores. Upon exposure to vapors of several organic molecules, the heat-treated sample of 2 adsorbs benzene and cyclohexene, but does not adsorb toluene, (o-, m-, and p-)xylenes, cycloheptatriene, or cyclohexane.     

Adsorption studies of a microporous phthalocyanine network polymer

The adsorption/desorption of N2 at 77 K and the adsorption from aqueous solution at 298 K of four organic probe molecules of different sizes (phenol, 4-nitrophenol, orange II, naphthol green B) were studied for a phthalocyanine network polymer of intrinsic microporosity (PIM) and for an activated carbon (Darco 20-40 mesh). N2 sorption analysis gave similar surface areas for the PIM and the carbon (610 and 545 m2 g(-1), respectively) but showed differences in pore size distribution, the PIM being essentially microporous (pore size < 2 nm), with a high proportion of ultramicropores (<0.7 nm), while the carbon had a broader pore size distribution, extending into the mesopore region. The carbon acted as an adsorbent for all the organic probe molecules studied, while the PIM was more selective, adsorbing the smaller molecules but rejecting the large dye naphthol green B. The PIM offers selectivity combined with a well-defined chemical structure incorporating catalytic sites.     

有机铵盐对FC-SAA表面活性及溶度的影响

测定了一系列有机铵盐与一种全氟烷磺酸盐１：１混合体系水 溶液的表面张力，由此研究有机铵盐对碳氟表面活性剂表面活性及溶度的影响，导出应用于此种混合体系的Ｇｉｂｂｓ吸附公式，并讨论了混合体系中两表面活性组分的表面分子相互作用和表面层的结构。     

Adsorption properties of iodine-doped activated carbon fiber

Iodine-doped activated carbon fibers (ACFs) were prepared by the iodine immersion method on pitch-based ACF. Then iodine-doped ACFs were heated in argon at 523 K for 4 h and at 673 K for 2 h. The iodine structure of the resultant iodine-doped ACFs was examined using X-ray photoelectron spectroscopy. The micropore structures were determined by N(2) adsorption at 77 K. The surface area and micropore volume of iodine-doped ACFs are less than those of pristine ACFs. However, the pore width does not change with the iodine doping. The effects of iodine doping on adsorption properties of ACFs for H(2)O and NO at 303 K were examined. The iodine doping affected remarkably the adsorptivities of ACFs for H(2)O and NO. In particular, iodine-doped ACFs treated at 673 K show enhanced adsorptivities for H(2)O and NO. This result suggests that iodine molecules doped on the micropores should be charged by heat treatment at 673 K.     

Ferrimagnetic Mixed-Valency and Mixed-Metal Tris(oxalato)iron(III) Compounds: Synthesis, Structure, and Magnetism

The synthesis and structural and magnetic characterization of 16 compounds AM(II)Fe(III)(C(2)O(4))(3) (A = N(n-C(3)H(7))(4), N(n-C(4)H(9))(4), N(n-C(5)H(11))(4), P(n-C(4)H(9))(4), P(C(6)H(5))(4), N(n-C(4)H(9))(3)(C(6)H(5)CH(2)), (C(6)H(5))(3)PNP(C(6)H(5))(3), As(C(6)H(5))(4); M(II) = Mn, Fe) are reported. X-ray powder diffraction profiles are indexed in R3c or its subgroup P6(5)22 or P6/mmm to derive unit cell constants. The structures of all the compounds consist of two-dimensional honeycomb networks [M(II)Fe(III)(C(2)O(4))(3)(-)](infinity). The M(II) = Fe compounds behave as ferrimagnets with T(c) between 33 and 48 K, but five exhibit a crossover from positive to negative magnetization near 30 K when cooled in a field of 10 mT. The compounds exhibiting this unusual magnetic behavior are those that have the highest T(c). Within the set N(n-C(n)()H(2)(n)()(+1))(4)Fe(II)Fe(III)(C(2)O(4))(3) (n = 3-5), T(c) increases with interlayer separation and the low-temperature magnetization changes from positive (n = 3) to negative (n = 4, 5). In the M = Mn(II) compounds, the in-plane cell parameter a(0) is approximately 0.03 ? greater than in the corresponding M = Fe(II) ones while the interlayer separation (c(0)/6) is on average 0.08 ? smaller. All members of the M(II) = Mn series have magnetic susceptibilities showing broad maxima at 55 K characteristic of two-dimensional antiferromagnetism, but the magnetization of several of the salts increases sharply below 27 K due to the onset of spin canting, the magnitude of which varies significantly with A.     

Molecular simulation of the adsorption and structure of benzene confined in mesoporous silicas

Grand Canonical Monte Carlo simulations are used to study the adsorption of benzene at 298 K in an atomistic cylindrical silica nanopore of a diameter 3.6 nm. The adsorption involves a transition from a partially filled pore (a two layers thick film at the pore surface) to a completely filled pore configuration. Strong layering of the benzene molecules at the pore surface is observed. It is found that the layering decays as the distance to the pore surface increases. The position of the peaks for the density of the C, H atoms and the center of mass of the molecules shows that benzene molecules prefer an orientation in which their ring is perpendicular to the pore surface. This result is corroborated by calculating orientational order parameters and examining the distribution of the distances between the H and C atoms of the benzene molecules and the H and O atoms of the silica substrate.     

氧化硅柱层状铁钛酸盐的合成和表征

通过先将K0.8Fe0.8Ti1.2O4与n-C6H13NH3Cl反应得到正己铵离子柱撑的层状铁钛酸盐, 然后再与NH2(CH2)3Si(OC2H5)3反应, 最后将所得产物在空气中焙烧可得到氧化硅柱层状铁钛酸盐。采用XRD, IR,TG/DTA, Mossbauer谱, X荧光分析以及比表面和孔径大小分布测定等手段对所得新材料进行了表征。结果表明: 所得二个氧化硅柱层状铁钛酸盐均具有较高的热稳定性(>650℃)和比表面(98.0m^2/g和163.8m^2/g), 平均孔径为1.82nm和1.90nm。     

Adsorption study of alkyl-silicas and methylsiloxy-silicas.

We report the synthesis and adsorption study of the lyophobic porous silicas. Four adsorbents were prepared and tested: (1) octyl-silica, (2) hexadecyl-silica, (3) bis(trimethylsiloxy)-silica, and (4) oligo(dimethylsiloxane)-silica. Octyl- and hexadecyl-silicas were prepared via the reaction of silica with (CH3)2NSi(CH3)2CnH(2n+1) (n=8 and 16), the reactions were carried under the optimized conditions yielding high bonding densities of alkyl groups approximately 2.9-3.0 groups/nm2 and highly uniform non-polar adsorbents. Bis(trimethylsiloxy)-silica was prepared via the reaction silica with ClSi(CH3)2(CH2)10Si(CH3)[OSi(CH3)3]2. Oligo(dimethylsiloxane)-silica was prepared via the reaction of silica with ClSi(CH3)2-[OSi(CH3)2]2-Cl. Adsorption of small organic compounds (n-alkanes, alkylbenzene, benzene, diethyl ether) was investigated using two methods, classical static adsorption and gas chromatography. Thermodynamic parameters (heat, Gibbs energy, and entropy) of the adsorption of organic compounds were studied as a function of the nature of adsorbate and of the nature of the bonded layer as well. The results obtained suggest penetration of the adsorbate molecules into the bonded layer and the importance of this process in the retention mechanism in gas chromatography. Energy of the dispersion interactions with the surface decreases in the following order: n-C16H33(CH3)2Si- > n-C8H17(CH3)2Si- > [(CH3)3SiO]2Si(CH3)-(CH2)10(CH3)2Si- > -[[(CH3)2SiO]2]x-(CH3)2Si-. Energy of the electrostatic and hydrogen bonding interactions with the surface, as assessed from the adsorption of benzene and diethyl ether molecules, decreases in the opposite direction, indicating that alkyl-silicas are less polar adsorbents than methylsiloxy-silicas.     

Novel superstructure of nondiscoid mesogens: uneven-parallel association of half-disk molecules, 3,4,5-trialkoxybenzoic anhydrides, to a columnar structure and its one-directionally geared interdigitation

Compact and simple nondiscoid mesogens, trialkoxybenzoic anhydrides 2-11 ((RO)(3)C(6)H(2)-CO-O-CO-C(6)H(2)(OR)(3), R = C(2)H(5), n-C(3)H(7), n-C(4)H(9), n-C(6)H(13), n-C(8)H(17), n-C(10)H(21), n-C(12)H(25), n-C(14)H(29), n-C(16)H(33), and (S)- and (R)-3,7-dimethyloctyl) were designed and synthesized, and their superstructures were investigated by polarized light microscopy, differential scanning calorimetry, calculation (MM2 and AM1), circular dichroism spectroscopy, and X-ray diffraction. As the result, in the cases of 5-9 and 11, the half-disk molecules in the liquid crystal phases were self-assembled by the dipole-dipole interaction between their carbonyl groups to a column in which the molecules were piled up in an alternately antiparallel manner, and the columns were interdigitated each other. The observed interdigitations were highly directional in the perpendicular direction to the column axis. In the case of compound 11 which has (S)- or (R)-3,7-dimethyloctyl groups, a helical organization of the molecules in the column was estimated from the peaks in the circular dichroism spectra. This is the first report of a one-directionally interdigitated columnar phase, and these compounds are the first liquid crystalline acid anhydrides. It was demonstrated that a -CO-O-CO- moiety is useful as a polar junction in liquid crystalline compounds.     

Pore with gate: enhancement of the isosteric heat of adsorption of dihydrogen via postsynthetic cation exchange in metal-organic frameworks

Three isostructural anionic frameworks {[(Hdma)(H(3)O)][In(2)(L(1))(2)]·4DMF·5H(2)O}(∞) (NOTT-206-solv), {[H(2)ppz][In(2)(L(2))(2)]·3.5DMF·5H(2)O}(∞) (NOTT-200-solv), and {[H(2)ppz][In(2)(L(3))(2)]·4DMF·5.5H(2)O}(∞) (NOTT-208-solv) (dma = dimethylamine; ppz = piperazine) each featuring organic countercations that selectively block the channels and act as pore gates have been prepared. The organic cations within the as-synthesized frameworks can be replaced by Li(+) ions to yield the corresponding Li(+)-containing frameworks {Li(1.2)(H(3)O)(0.8)[In(2)(L(1))(2)]·14H(2)O}(∞) (NOTT-207-solv), {Li(1.5)(H(3)O)(0.5)[In(2)(L(2))(2)]·11H(2)O}(∞) (NOTT-201-solv), and {Li(1.4)(H(3)O)(0.6)[In(2)(L(3))(2)]·4acetone·11H(2)O}(∞) (NOTT-209-solv) in which the pores are now unblocked. The desolvated framework materials NOTT-200a, NOTT-206a, and NOTT-208a display nonporous, hysteretic and reversible N(2) uptakes, respectively, while NOTT-206a and NOTT-200a provide a strong kinetic trap showing adsorption/desorption hysteresis with H(2). Single crystal X-ray analysis confirms that the Li(+) ions are either tetrahedrally (in NOTT-201-solv and NOTT-209-solv) or octahedrally (in NOTT-207-solv) coordinated by carboxylate oxygen atoms and/or water molecules. This is supported by (7)Li solid-state NMR spectroscopy. NOTT-209a, compared with NOTT-208a, shows a 31% enhancement in H(2) storage capacity coupled to a 38% increase in the isosteric heat of adsorption to 12 kJ/mol at zero coverage. Thus, by modulating the pore environment via postsynthetic cation exchange, the gas adsorption properties of the resultant MOF can be fine-tuned. This affords a methodology for the development of high capacity storage materials that may operate at more ambient temperatures.