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Sulfur dioxide (SO2) is a harmful acidic gas generated from power plants and fossil fuel combustion and represents a significant health risk and threat to the environment. Benzimidazole-linked polymers (BILPs) have emerged as a promising class of porous solid adsorbents for toxic gases because of their chemical and thermal stability as well as the chemical nature of the imidazole moiety. The performance of BILPs in SO2capture was examined by synergistic experimental and theoretical studies. BILPs exhibit a significantly high SO2uptake of up to 8.5 mmol g–1at 298 K and 1.0 bar. The density functional theory (DFT) calculations predict that this high SO2uptake is due to the dipole–dipole interactions between SO2and the functionalized polymer frames through O2S(δ+)···N(δ–)-imine and O═S═O(δ–)···H(δ+)-aryl and intermolecular attraction between SO2molecules (O═S═O(δ–)···S(δ+)O2). Moderate isosteric heats of adsorption (Qst≈ 38 kJ mol–1) obtained from experimental SO2uptake studies are well supported by the DFT calculations (≈40 kJ mol–1), which suggests physisorption processes enabling rapid adsorbent regeneration for reuse. Repeated adsorption experiments with almost identical SO2uptake confirm the easy regeneration and robustness of BILPs. Moreover, BILPs possess very high SO2adsorption selectivity at low concentration over carbon dioxide (CO2), methane (CH4), and nitrogen (N2): SO2/CO2, 19–24; SO2/CH4, 118–113; SO2/N2, 600–674. This study highlights the potential of BILPs in the desulfurization of flue gas or other gas mixtures through capturing trace levels of SO2.

Efficient management of radionuclides that are released from various processes in the nuclear fuel cycle is of significant importance. Among these nuclides, radioactive iodine (mainly 129I and 131I) is a major concern due to the risk it poses to the environment and to human health; thus, the development of materials that can capture and safely store radioactive iodine is crucial. Herein, a novel silver–thione-functionalized zeolitic imidazole framework (ZIF) was synthesized via postsynthetic modification and assessed for its iodine uptake capabilities alongside the parent ZIF-8 and intermediate materials. A solvent-assisted ligand exchange procedure was used to replace the 2-methylimidazole linkers in ZIF-8 with 2-mercaptoimidazole, forming intermediate compound ZIF-8 = S, which was reacted with AgNO3to yield the ZIF-8 = S–Ag+composite for iodine uptake. Despite possessing the lowest BET surface area of the derivatives, the Ag-functionalized material demonstrated superior I2adsorption in terms of both maximum capacity (550 g I2/mol) and rapid kinetics (50% loading achieved in 5 h, saturation in 50 h) compared to that of our pristine ZIF-8, which reached 450 g I2/mol after 150 h and 50% loading in 25 h. This improvement is attributed to the presence of the Ag+ions, which provide a strong chemical driving force to form a stable Ag–I species. The results of this study contribute to a broader understanding of the strategies that can be employed to engineer adsorbents with robust iodine uptake behavior.

The selective capture of carbon dioxide over nitrogen and hydrogen is of great industrial interest in flue gas and hydrogen purification, respectively. Microporous adsorbents are highly suitable materials to preferentially adsorb gases. In particular, porous organic cages (POCs) with tunable hierarchically ordered micropores, high surface area, and thermodynamic affinity for CO2make them appealing candidates for these applications. Herein, we demonstrate that two prototypical POCs denoted as CC3 and CC2 with a limiting pore aperture of 3.6 Å can selectively separate CO2from N2and H2. For CC3 adsorption selectivities as high as ∼8 and ∼20 for CO2/N2and CO2/H2, respectively, were observed. For CC2 adsorption selectivities as high as ∼9 and ∼35 for CO2/N2and CO2/H2, respectively, were observed. Interestingly, the adsorption selectivity of the studied gases correlated linearly with polarizability ratio.

PoreMatMod.jlis a free, open-source, user-friendly, and documented Julia package for modifying crystal structure models of porous materials such as metal–organic frameworks (MOFs). PoreMatMod.jlfunctions as a find-and-replace algorithm on crystal structures by leveraging (i) Ullmann’s algorithm to search for subgraphs of the crystal structure graph that are isomorphic to the graph of a query fragment and (ii) the orthogonal Procrustes algorithm to align a replacement fragment with a targeted substructure of the crystal structure for installation. The prominent application of PoreMatMod.jlis to generate libraries of hypothetical structures for virtual screenings. For example, one can install functional groups on the linkers of a parent MOF, mimicking postsynthetic modification. Other applications of PoreMatMod.jlto modify crystal structure models include introducing defects with precision and correcting artifacts of X-ray structure determination (adding missing hydrogen atoms, resolving disorder, and removing guest molecules). The find-and-replace operations implemented by PoreMatMod.jlcan be applied broadly to diverse atomistic systems for various in silicostructural modification tasks.

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to study noble gas (i.e., He, Kr, and Xe) adsorption in metal-oxide frameworks (MOFs). To study the adsorption of infrared (IR)-inactive noble gases, we monitored the intensity of MOF stretching vibrations as a function of gas pressure using the DRIFTS spectra. Specific and nonspecific adsorption sites were identified in Ni/DOBDC (DOBDC = 1,4-dioxido-2,5-benzenedicarboxylate) and HKUST-1 (HKUST = Hong Kong University of Science and Technology) MOFs after noble gas adsorption, and the results were consistent with those obtained from single-crystal synchrotron X-ray diffraction (XRD) experiments and results published in the literature. Our results demonstrate that the DRIFTS technique can be an alternative approach for locating gas adsorption sites in MOFs. The adsorption selectivity of Xe/Kr for the two MOFs had qualitatively related to the peak saturation pressure in the DRIFTS spectrum, and the results are consistent with those obtained from isotherm data. In addition to the Xe adsorption process, we investigated the Xe desorption process by using the DRIFTS technique for HKUST-1 to validate the analysis of DRIFTS spectral data. We also studied competitive adsorption between Xe and trace amounts of water in the Ni/DOBDC.

Two lanthanide-containing porous coordination polymers, [Ln2(bpdc)6(phen)2]·nH2O (1) and [Ln2(bpdc)6(terpy)2]·3H2O (2) (Ln = Pr, Nd, or Sm–Dy; bpdc: 2,2′-bipyridine-5,5′-dicarboxylic acid; phen: 1,10-phenanthroline; and terpy: 2,2′:6′,2″-terpyridine), have been hydrothermally synthesized and structurally characterized by powder and single-crystal X-ray diffraction. Crystallographic analyses reveal that compounds 1and 2feature Ln3+-containing dimeric nodes that form a porous two-dimensional (2D) and nonporous three-dimensional (3D) framework, respectively. Each material is stable in aqueous media between pH 3 and 10 and exhibits modest thermal stability up to ∼400 °C. Notably, a portion of the phen and bpdc ligands in 1can be removed thermally, without compromising the crystal structure, causing the surface area and pore volume to increase. The optical properties of 1and 2with Gd3+, Sm3+, Tb3+, and Eu3+are explored in the solid state using absorbance, fluorescence, and lifetime spectroscopies. The analyses reveal a complex blend of metal and ligand emission in the materials containing Sm3+and Tb3+, while those featuring Eu3+are dominated by intense metal-based emission. Compound 1with Eu3+shows promise for the capture and detection of the uranyl cation (UO2)2+from aqueous media. In short, uranyl capture is observed at pH 4, and the adsorption thereof is detectable via vibrational and fluorescence spectroscopies and colorimetrically as the off-white color of 1turns yellow with uptake. Finally, both 1and 2with Eu3+produce bright red emission upon irradiation with Cu Kα X-ray radiation (8.04 keV) and are candidate materials for applications in solid-state scintillation.

The unique features of metal–organic frameworks (MOFs), such as their large surface areas and diversity of structures, make them suitable for a broad range of applications including storage, separation, and sensing of gases. Among all the MOFs, Mg-MOF-74 with the highest CO2uptake at 1 bar and 25 °C would be particularly beneficial for CO2-related applications. One of the most critical enabling technologies for implementing Mg-MOF-74 is the preparation of dense and continuous films that would maximize the sorption behaviors. However, Mg-MOF-74 thin films present significant challenges in demonstrating large-scale coatings. Herein, we demonstrate for the first time high-quality Mg-MOF-74 films synthesized viaa vapor-assisted crystallization (VAC) process. The VAC process described herein provides dense and highly crystalline layers of the Mg-MOF-74 thin film with a low coefficient of variation of film thickness below 7%. By minimizing the solvent use, the VAC process is also more environmentally friendly than conventional techniques. In this work, we first optimized a precursor solution for the VAC process and then investigated the effects of synthesis temperature, time, and droplet volume on the growth, crystallinity, and thickness of VAC Mg-MOF-74 films. The porosity of the MOF film was assessed by measuring the CO2uptake at room temperature and 1 bar. The obtained VAC Mg-MOF-74 films possess a well-defined microporosity, as deduced from CO2adsorption studies viaquartz crystal microbalance (QCM) and comparison with bulk Mg-MOF-74 reference data. Furthermore, CO2cyclic adsorption–desorption experiments on the VAC Mg-MOF-74 films showed scaled uptakes to a wide range of CO2concentration without showing significant variations in the baseline. We specifically demonstrate how the film’s quality of the MOF affects adsorption behavior of CO2on VAC Mg-MOF-74 and drop-cast Mg-MOF-74 films.

Directed synthesis promises control over architecture and function of framework materials. In practice, however, designing such syntheses requires a detailed understanding of the multistep pathways of framework formations, which remain elusive. By identifying intermediate coordination complexes, this study provides insights into the complex role of a structure-directing agent (SDA) in the synthetic realization of a promising material. Specifically, a novel molecular intermediate was observed in the formation of an indium zeolitic metal–organic framework (ZMOF) with a sodalite topology. The role of the imidazole SDA was revealed by time-resolved in situ powder X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS).

Mechanically robust forms of HKUST-1 metal–organic frameworks (MOFs) were fabricated by embedding the MOF crystals in a passive polyacrylonitrile (PAN) matrix at different MOF loadings of 10–90 mass %. PAN is highly porous and acts as a scaffold that holds the active MOF adsorbent in place. These MOF–PAN composites were then evaluated for capturing Xe. Data presented herein show that the PAN matrix does not notably interfere with the Xe capture process, where the Xe capacities scale somewhat linearly with the increase in MOF loadings within the composites. Also, γ radiation exposures to the composites revealed that they are highly tolerant to these types of radiation fields.

Metal–organic framework (MOF) heterostructures exhibit unique properties beyond those of individual components, but their design requires an understanding of energetic and kinetic controls at MOF–substrate interfaces. Although the structural relationship has been widely used in heterostructure design, it overlooks the interplay between the organic ligand and the substrate which controls the kinetics and energetics of growth of the final structure. Herein we used zeolitic imidazolate frameworks (ZIF-8) on ZnO as a model system to evaluate this interplay via in situmonitoring and simulations. Our results demonstrate multiple roles of the 2-methyl-imidazole (2-MIM) ligand as “dissolution-promoter”, “step-pinner”, and “terrace-binder” on the ZnO (001) face and “dissolution-promoter” and “terrace-binder” on the ZnO (100) face. Through these multiple face-specific roles, 2-MIM modulates ZnO dissolution kinetics and, hence, the Zn2+release rate, tuning local supersaturations that dictating the characteristic ZIF-8 crystallization kinetics on different substrate faces. The critical thickness for transition from 2D to 3D growth is dictated by competition between interfacial and strain energies. The atomic-scale mechanism of the coupled substrate dissolution and MOF growth, mediated by selective linker–substrate binding, furnishes a new synthesis pathway for other complex heterostructures.

Postsynthetic modification (PSM) in metal–organic frameworks (MOFs) can introduce multiple functionalities and alter the structural function for the desired application. However, the PSM of the coordination site faces the challenges of structural collapse or incompatibility between the original metal site and the newly formed coordination group. Herein, we developed a novel concept of introducing “primary” and “secondary” nodes, coexisting in a water-stable, Zr-based heterometallic MOF, [Zr6(μ3-OH)8(OH)8][Cu4I(L1)4]2(1-SH-a, H2L1= 6-mercaptopyridine-3-carboxylic acid). The postsynthetic oxidation at the coordination site was successfully achieved in the secondary nodes [Cu4I(L1)4]4–, while the robust primary nodes [Zr6(μ3-OH)8(OH)8]8+stabilized the whole framework to form [Zr6(μ3-OH)8(OH)8][(Cu0.44ICu0.56II(OH)0.56)4(L2)4]2(1-SO3H, H2L2= 6-sulfonicotinic acid). Attempts to directly synthesize 1-SO3Hthrough the reactions of Zr(IV), Cu(II), and H2L2failed. Furthermore, the PSM of 1-SH-ato form 1-SO3Hwas utilized to tune the catalytic behaviors toward the styrene oxide ring-opening reaction to give an improved regioselectivity of the primary alcohol (A) of ∼99% compared with that of 1-SH-a(∼71%).

Herein we report the first example of a metal–organic framework (MOF) in which the location of Li+ions trapped in the porous confinement can be unambiguously defined by single-crystal X-ray diffraction. Furthermore, the Li+-doped MOF shows significant enhancement in gas uptake as well as selective adsorption of CO2over CH4.

A combined Monte Carlo (MC) simulation and periodic density functional theory (DFT) study of CO2sorption was performed in SIFSIX-3-M(M = Fe, Co, Ni, Cu, Zn), a family of hybrid ultramicroporous materials (HUMs) that consist of M2+ions coordinated to pyrazine ligands and are pillared with SiF62–(“SIFSIX”) anions. Grand canonical Monte Carlo (GCMC) simulations of CO2sorption in all five SIFSIX-3-Mvariants produced isotherms that are in good agreement with the corresponding experimental measurements. The theoretical isosteric heats of adsorption (Qst) for CO2as obtained through canonical Monte Carlo (CMC) simulations are also in close agreement with the experimental values. Consistent with experiment, the simulations generated the following trend in the CO2Qst: SIFSIX-3-Cu> SIFSIX-3-Ni> SIFSIX-3-Co> SIFSIX-Zn> SIFSIX-3-Fe. The magnitudes of the theoretical Qstand relative trend were further supported by periodic DFT calculations of the adsorption energy for CO2within the respective HUMs. We attribute the observed Qsttrend in SIFSIX-3-Mto their differences in pore size and lattice parameters. Specifically, the sorption energetics decrease with increasing pore size and a/blattice constant. Simulations of CO2sorption in SIFSIX-3-Curesulted in different profiles for the radial distribution function (g(r)) and dipole distribution than within the other analogues due to the smaller pore size and much shorter a/bunit cell lengths of the crystal structure; this is a direct consequence of the Jahn–Teller effect. Although these HUMs are isostructural, notable differences in the classical energy contributions for CO2sorption were observed from the GCMC simulations. Overall, this study demonstrates that the CO2Qstin SIFSIX-3-Mcan be controlled by the choice of the saturated metal, with values ranging from 42 to 54 kJ mol–1.

Exceptionally stable ultramicroporous C–C-bonded porous organic frameworks (IISERP-POF6, 7, 8) have been prepared using simple Friedel–Crafts reaction. These polymers exhibit permanent porosity with a Brunauer–Emmett–Teller surface area of 645–800 m2/g. Xe/Kr adsorptive separation has been carried out with these polymers, and they display selective Xe capture (s(Xe/Kr) = 6.7, 6.3, and 6.3) at 298 K and 1 bar pressure. Interestingly, these polymers also show remarkable Xe/N2(s(Xe/N2) = 200, 180, and 160 at 298 K and 1 bar) and Xe/CO2selectivity (s(Xe/CO2) = 5.6, 7.4, and 5.6) for a 1:99 composition of Xe–N2/Xe–CO2. Selective removal of Xe at such low concentrations is extremely challenging; the observed selectivities are higher compared to those observed in porous carbons and metal–organic frameworks. Breakthrough studies were performed using the composition relevant to the nuclear off-gas mixture with the polymers, and we find that the polymers hold Xe for a longer time in the column, which illustrates the Xe/Kr separation performance under dynamic conditions.

Selective adsorptive capture and separation of chemically inert krypton (Kr) and xenon (Xe) noble gases with very low ppmv concentrations in air and industrial off-gases constitute an important technological challenge. Here, using a synergistic combination of experiment and theory, the microporous crystalline vanadomolybdates (MoVOx) as highly selective Kr sorbents are studied in detail. By varying the Mo/V ratios, we show for the first time that their one-dimensional (1D) pores can be fine-tuned for the size-selective adsorption of Kr over the larger Xe with selectivities reaching >100. Using extensive electronic structure calculations and grand canonical Monte Carlo simulations, the competition between Kr uptake with CO2and N2was also investigated. As most materials reported so far are selective toward the larger, more polarizable Xe than Kr, this work constitutes an important step toward robust Kr-selective sorbent materials. This work highlights the potential use of porous crystalline transition metal oxides as energy-efficient and selective noble gas capture sorbents for industrial applications.

Several low-dimensional Ni/Ni−Cd complexes containing the N2O2donor tetradentate symmetrical Schiff base ligand bis(acetylacetone)ethylene-diamine (sy-H2L2), namely, [Ni(sy-L2)]2·HLa·ClO4(2), (HLa)2·(ClO4)·(NO3) (3), [Ni(sy-L2)X]2](4,4′-bipy) (where La= 5,7-dimethyl-3,6-dihydro-2H-1,4-diazepine, X = ClO4(4), X = NO3(5), [Ni(sy-L2)Cd(SCN)2]n(6) and [Ni(sy-L2)·Cd(N3)2]n(7), have been synthesized from [Ni(sy-L2)]2·H2O (1). Complex 2is a three-component discrete assembly generated from a (HLa)+moiety bridged with a [Ni(sy-L2)] unit and ClO4−anion. A solution containing complex 2and Cd(NO3)2results in a mixture of 1and 3. Further recrystallization of 1and 3with various auxiliary ligands provides coordination complexes 4−7stabilized by weak hydrogen bonds in which 6and 7represent the first one-dimensional heteronuclear complexes based on the symmetric acacen-base Schiff base ligand.

Adsorption isotherms of pure gases present in flue gas including CO2, N2, SO2, NO, H2S, and water were studied using prussian blues of chemical formula M3[Co(CN)6]2·nH2O (M = Co, Zn) using an HPVA-100 volumetric gas analyzer and other spectroscopic methods. All the samples were characterized, and the microporous nature of the samples was studied using the BET isotherm. These materials adsorbed 8−10 wt % of CO2at room temperature and 1 bar of pressure with heats of adsorption ranging from 200 to 300 Btu/lb of CO2, which is lower than monoethanolamine (750 Btu/lb of CO2) at the same mass loading. At high pressures (30 bar and 298 K), these materials adsorbed approximately 20−30 wt % of CO2, which corresponds to 3 to 5 molecules of CO2per formula unit. Similar gas adsorption isotherms for SO2, H2S, and NO were collected using a specially constructed volumetric gas analyzer. At close to 1 bar of equilibrium pressure, these materials sorb around 2.5, 2.7, and 1.2 mmol/g of SO2, H2S, and NO. In particular, the uptake of SO2and H2S in Co3[Co(CN)6]2is quite significant since it sorbs around 10 and 4.5 wt % at 0.1 bar of pressure. The stability of prussian blues before and after trace gases was studied using a powder X-ray diffraction instrument, which confirms these materials do not decompose after exposure to trace gases.

Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of 85Kr and 129I2due to their volatility and long half-life. Efficient capture of 129I2(t1/2= 15.7 × 106years) from the nuclear waste stream can help reduce the risk of releasing I2radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I2adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account. Moisture-stable porous metal organic frameworks that can selectively adsorb I2in the presence of water vapor are thus of great interest. Herein, we report on the I2adsorption capacity of two microporous metal organic frameworks at both dry and humid conditions. Single-crystal X-ray diffraction and Raman spectroscopy reveal distinct sorption sites of molecular I2within the pores in proximity to the phenyl- and phenol-based linkers stabilized by the I···π and I···O interactions, which allow selective uptake of iodine.

High-surface-area molybdenum sulfide (MoSx) and antimony sulfide (SbSx) chalcogels were studied for Xe/Kr gas separation. The intrinsic soft Lewis basic character of the chalcogel framework is a unique property among the large family of porous materials and lends itself to a potential new approach toward the selective separation of Xe over Kr. Among these chalcogels, MoSxshows the highest Xe and Kr uptake, reaching 0.69 mmol g–1(1.05 mmol cm–3) and 0.28 mmol g–1(0.42 mmol cm–3) respectively, at 273 K and 1 bar. The corresponding isosteric heat of adsorption at zero coverage (Qst0) is 22.8 and 18.6 kJ mol–1and both are the highest among the selected chalcogels. The IAST (10:90) Xe/Kr selectivity at 273 K for MoSxis 6.0, whereas for SbSxchalcogels, it varies in the range 2.0–2.8. The higher formal charge of molybdenum, Mo4+, in MoSxversus that of antimony, Sb3+, in SbSxcoupled with its larger atomic size could induce higher polarizability in the MoSxframework and therefore higher Xe/Kr selectivity.

The synthetic approaches for fine-tuning the structural properties of coordination polymers or metal organic frameworks have exponentially grown during the past decade. This is due to the control over the properties of the resulting structures such as stability, pore size, pore chemistry and surface area for myriad possible applications. Herein, we present a new class of porous materials called Coordination Covalent Frameworks (CCFs) that were designed and effectively synthesized using a two-step reticular chemistry approach. During the first step, trigonal prismatic molecular building block was isolated using 4-aminobenazoic acid and Cr (III) salt, subsequently in the second step the polymerization of the isolated molecular building blocks (MBBs) takes place by the formation of strong covalent bonds where small organic molecules can connect the MBBs forming extended porous CCF materials. All the isolated CCFs were found to be permanently porous while the discrete MBB were nonporous. This approach would inevitably open a feasible path for the applications of reticular chemistry and the synthesis of novel porous materials with various topologies under ambient conditions using simple organic molecules and versatile MBBs with different functionalities that would not be possible using the traditional one-step approach.

Combined application of in situX-ray diffraction (XRD) and differential scanning calorimetry (DSC) is a novel technique for rapidly evaluating the suitability of microporous materials for postcombustion CO2capture. Further, while many microporous materials show promise for CO2capture, most are not evaluated in the presence of water vapor, a major component of postcombustion flue gas. As a demonstration of the versatility of XRD-DSC techniques, representatives of the classes of materials typically proposed for CO2capture, zeolites, and metal–organic frameworks (MOFs) were studied: zeolite NaX, Ni-MOF-74 [Ni2(dobdc); dobdc = 2,5-dihydroxyterephthalate], ZIF-7 [ZIF: zeolitic imidazole framework, Zn(phim)2; phim: benzimidazole], and SBMOF-1 [Ca(sdb); sdb: 4,4′-sulfonyldibenzoate]. Although NaX and Ni-MOF-74 show very high affinity toward CO2under idealized dry conditions, they are also very sensitive to the presence of water vapor and experience significant performance loss above 25% relative humidity (RH) at room temperature. Relative to NaX and Ni-MOF-74, ZIF-7 and SBMOF-1 show strong CO2affinity even in the presence of 75% RH and may be more ideally suited for postcombustion flue gas CO2capture than compounds with unsaturated metal sites. XRD-DSC is particularly powerful for evaluating the consequences of framework flexibility, with XRD providing the signature indicative of the structural rearrangement and the DSC providing the enthalpies of adsorption for each structure. This kind of detailed energy evaluation is not possible with other noncalorimetric methods.

Nanoscale porous coordination polymers were synthesized using simple wet chemical method. The effect of various polymer surfactants on colloidal stability and shape selectivity was investigated. Our results suggest that the nanoparticles exhibited significantly improved adsorption kinetics compared to bulk crystals due to decreased diffusion path lengths and preferred crystal plane interaction.

A hierarchically structured nitrogen-doped porous carbon is prepared from a nitrogen-containing isoreticular metal-organic framework (IRMOF-3) using a self-sacrificial templating method. IRMOF-3 itself provides the carbon and nitrogen content as well as the porous structure. For high carbonization temperatures (950 °C), the carbonized MOF required no further purification steps, thus eliminating the need for solvents or acid. Nitrogen content and surface area are easily controlled by the carbonization temperature. The nitrogen content decreases from 7 to 3.3 at % as carbonization temperature increases from 600 to 950 °C. There is a distinct trade-off between nitrogen content, porosity, and defects in the carbon structure. Carbonized IRMOFs are evaluated as supercapacitor electrodes. For a carbonization temperature of 950 °C, the nitrogen-doped porous carbon has an exceptionally high capacitance of 239 F g–1. In comparison, an analogous nitrogen-free carbon bears a low capacitance of 24 F g–1, demonstrating the importance of nitrogen dopants in the charge storage process. The route is scalable in that multi-gram quantities of nitrogen-doped porous carbons are easily produced.

It is important to capture carbon dioxide from flue gas, which is considered one of to be the main cause of global warming. CO2/N2separation by novel adsorbents is a promising method for reducing CO2emission. Meanwhile, water effects on CO2adsorption and CO2/N2selectivity is critical to enable utilization of the adsorbents in practical applications. In this paper, Ni/DOBDC (Ni-MOF-74 or CPO-27-Ni) was synthesized through a solvothermal reaction, and the pellet sample was used in a fixed-bed CO2/N2breakthrough study with and without H2O. The Ni/DOBDC pellet has a high CO2capacity of 3.74 mol/kg at 0.15 bar and a high CO2/N2selectivity of 38, which is much higher than those of reported metal–organic frameworks and zeolites under dry conditions. Trace amounts of water can affect CO2adsorption capacity as well as CO2/N2selectivity for the Ni/DOBDC. However, Ni/DOBDC can retain a significant CO2capacity of 2.2 mol/kg and a CO2/N2selectivity of 22 at 0.15 bar CO2with 3% RH water. These results indicate a promising future for use of the Ni/DOBDC in capturing CO2from flue gas.

The metal–organic framework copper–1,3,5‐benzenetricarboxylate (Cu‐BTC) was evaluated for its ability to selectively interact with Lewis‐base analytes by examining retention on gas‐chromatographic columns packed with Chromosorb W HP that contained 3.0% SE‐30 along with various loadings of Cu‐BTC. Scanning electron microscopy images of the support material showed the characteristic Cu‐BTC crystals embedded in the SE‐30 coating on the diatomaceous support. The results indicated that the Cu‐BTC‐containing stationary phase had limited thermal stability (220°C) and strong general retention for analytes. Kováts index calculations showed selective retention (amounting to about 300 Kováts units) relative to n‐alkanes for many small Lewis‐base analytes on a column that contained 0.75% Cu‐BTC compared with an SE‐30 control. Short columns that contained lower loadings of Cu‐BTC (0.10%) allowed elution of nitroaromatics; however, selectivity was not observed for aromatic compounds (including nitroaromatics) or nitroalkanes. Observed retention characteristics are discussed.

The efficient removal of pertechnetate (TcO4–) anions from liquid waste or melter off-gas solution for an alternative treatment is one of the promising options to manage 99Tc in legacy nuclear waste. Safe immobilization of 99Tc is of major importance because of its long half-life (t1/2= 2.13 × 105yrs) and environmental mobility. Different types of inorganic and solid-state ion-exchange materials have been shown to absorb TcO4–anions from water. However, both high capacity and selectivity have yet to be achieved in a single material. Herein, we show that a protonated version of an ultrastable zirconium-based metal–organic framework can adsorb perrhenate (ReO4–) anions, a nonradioactive surrogate for TcO4–, from water even in the presence of other common anions. Synchrotron-based powder X-ray diffraction and molecular simulations were used to identify the position of the adsorbed ReO4–(surrogate for TcO4–) molecule within the framework.

Background: Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 – 100 nm in diameter have dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for early detection of diseases such as cancer. Surface functionalization has expanded further the potential of nanoparticles as probes for molecular imaging. Objective: To summarize emerging research of nanoparticles for biomedical imaging with increased selectivity and reduced nonspecific uptake with increased spatial resolution containing stabilizers conjugated with targeting ligands. Methods: This review summarizes recent technological advances in the synthesis of various nanoparticle probes, and surveys methods to improve the targeting of nanoparticles for their application in biomedical imaging. Conclusion: Structural design of nanomaterials for biomedical imaging continues to expand and diversify. Synthetic methods have aimed to control the size and surface characteristics of nanoparticles to control distribution, half-life and elimination. Although molecular imaging applications using nanoparticles are advancing into clinical applications, challenges such as storage stability and long-term toxicology should continue to be addressed.

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The crystal chemistry of molecular complexes of several trigonal donor molecules with the trigonal acceptor 1,3,5-trinitrobenzene, TNB, is reported. Generally, replacement of a moiety by another of similar shape and size does not change the overall packing. The 1:1:1 (triphenylisocyanurate)·(TNB)·(benzene) solvate is isostructural to the corresponding 1:1:1 thiophene solvate, confirming the so-called benzene–thiophene exchange rule. The 1:1 complex of tris-2,4,6-(4-methylphenyl)-1,3,5-triazine and TNB is layered and the layers have quasi-trigonal symmetry. The triazine ring may be replaced by a phenyl ring without any change in the crystal structure. Thus, 1,3,5-tris(4-methylphenyl)benzene and TNB form an isostructural 1:1 complex. Such shape/size exchange may be further explored in the 1:1 complex of 1,3,5-tris[5-(2-chlorothienyl)]benzene and TNB. Here both phenyl–thienyl and chloro–methyl exchanges are simultaneously possible and yet another isostructural complex is obtained. Finally, the 1:1 complex of 1,3,5-tris(2-thienyl)benzene and TNB is also found to have a very similar structure. However, when 1,3,5-triphenylbenzene and TNB are taken in 1:1 ratio in solution, the result is a 1:3 molecular complex. This is unexpected in view of the phenyl–thienyl exchange rule, and some rationalisation is provided for the unusual formation of this 1:3 complex. Many of these structures are pertinent from the viewpoint of carry-over of trigonal molecular symmetry into the crystal, a contemporary theme in the engineering of crystal structures for octupolar non-linear optical applications, while ready access to the 1,3,5-trisubstituted benzenes for this study was made possible by a general and efficient protocol for the synthesis of these compounds from the corresponding acetyl aromatics.

Based on our earlier observation that para-halogenated phenoxy triazines self-assemble as hexagonal nanoporous frameworks, this study deals with the inclusion of structurally related guest species in the one-dimensional channels of the title host compounds. A systematic analysis of six isomorphous, X-ray crystal structures (space group P63/m) provides valuable information of wide-ranging implications in host–guest chemistry: (1) construction of a host lattice with weak intermolecular interactions; (2) correlation of guest-size and host–channel area with order/disorder in the host; (3) role of molecular symmetry and multi-point hydrogen bond recognition for ordered guest species; (4) unusual structural behaviour and properties of guests constrained in a narrow channel. Lastly, a ternary adduct crystal shows an intricate hydrogen bonding network in the polar space group R3c with a super-cell of c=63.67Å.

Large multicomponent nanospheroid arrays consisting of six C-pentylpyrogallol[4]arene molecules and 12 Ga3metal-ions which in turn enclose 1150 Å3of chemical space are reported.

The low density polymorph of the well-known host p-tert-butylcalix4arene absorbs more methane than p-tert-pentylcalix4arene at room temperature and 1 atm pressure, but the order of absorption is reversed at 38 atm with p-tert-pentylcalix4arene absorbing more.

A well-known host compound readily absorbs methane at room temperature and pressures of one atmosphere and lower.

We have studied the hydrogen sorption on three well-known organic hosts that possess vacant lattice voids large enough to accommodate H2molecules.

A low-density polymorph of the well-known host compound p-tert-butylcalix4arene undergoes subtle structural changes when heated and cooled.

1,3-Dibromo-2,4,6-trinitrobenzene (DBTNB), a two-dimensional charge transfer hyperpolarisable chromophore, crystallises in the non-centrosymmetric space group C2 in perfect polar order leading to an intense powder SHG signal at 1.06 μm.

The title molecule forms a honeycomb network of molecular and nitro-trimer synthons with guest species included in the hexagonal voids.

Conformational flexibility in a symmetrical tris-phenol leads to close packed structures that are also characterised by an extended though finite cooperative chain of hydrogen bonds.

The title compound, 1,3,5‐tris(2‐cyano­ethyl)‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione, C12H12N6O3, forms a layered structure stabilized by C—H⋯O and C—H⋯N hydrogen bonds.

Adsorption isotherms of pure gases present in flue gas including CO2, N2, SO2, NO, H2S, and H2O are measured for M3[Co(CN)6]2·nH2O (M: Co, Zn).

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