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This paper evaluates the effect of different synthesis conditions on the structural properties of the porous metal–organic frameworks MIL-53(Al) produced by the microwave method at different reaction temperatures (120, 150, and 180 °C) and times (30, 180 min). The morphologies, chemical contents and crystal structures of the synthesized samples were determined by the SEM-EDS and XRD methods, respectively. The structural properties of MIL-53(Al)s were analysed according to isotherm data obtained from nitrogen gas adsorption by applying the Brunauer–Emmett–Teller (BET), Langmuir, Dubinin–Radushkevich (DR), t-plot, Barrett–Joyner–Halenda (BJH) and quenched solid density functional theory (QSDFT) methods, as well as the new numerical clustering-based adsorption analysis (LBET) method, which is a unique numerical method that provides advanced assessment for porous structures. The LBET analysis showed that the MIL-53(Al) sample at a reaction temperature of 180 °C for 30 min has the best adsorption properties, with the highest volume of the first adsorbed layer and the highest value of the energy parameter for higher layers. Due the LBET method, it was possible to evaluate the porous structure of the MIL-53(Al) samples with high precision and reliability, and thus to determine the precise influence of the conditions of their preparation on the formation of their structure. In turn, based on the shapes of the pore size distributions (PSD), the materials analysed have very similar PSD, with only the MIL-35(AL)S1 sample having a significantly lower PSD height. In conclusion, attention was paid to the necessity of complex evaluation of adsorbent properties, taking into account not only their adsorption properties but also their mechanical and functional properties, as well as production costs and the impact of adsorbent production and utilization on the environment. [ABSTRACT FROM AUTHOR]

Zeolite LTA, with high porosity and uniform pore distribution, has been widely used in the gas adsorption field. In this paper, a 1.38 nm thick two-dimensional zeolite LTA was synthesized from kaolin, changing the cubic morphology of the traditional zeolite LTA. SEM and TEM images showed that the zeolite LTA exhibited a lamellar structure. In a comparative experiment with CO2 adsorption at different temperatures, the 2D zeolite LTA with a large specific surface area could capture more CO2 than the conventional 3D zeolite LTA. In addition, the CO2/CH4 selectivity of the 2D Zeolite LTA was 76.78 at 298 K. [ABSTRACT FROM AUTHOR]

The surface states of gas sensing materials based on oxide semiconductors are closely related to their sensing dynamics. In this work, using surface engineering, p-type ZnCo2O4 architectures are prepared through a feasible hydrothermal strategy followed by subsequent annealing treatment and are applied for the detection of inert xylene gas. The as-prepared ZnCo2O4 architecture (ZCO-300) exhibits a higher response and selectivity toward xylene gas at a working temperature of 170 °C. Moreover, the ZCO-300 sensor also presents superior stability/reliability, good moisture resistance and a low detection limit of 0.1 ppm. The larger number of oxygen vacancy defects and higher specific surface area in ZCO-300 not only promote the catalytic oxidation of xylene gas by p-type semiconductor ZnCo2O4, but also provide more gas adsorption sites and surface reaction sites on sensing material surfaces, thereby endowing ZCO-300 with superior xylene gas sensing properties. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) was used to investigate the adsorption of twenty-four gases (SiH4, H2, Cl2, F2, CF4, CH4, CF2Cl2, N2, CHF3, OCS, N2O, AsH3, CH3Cl, COCl2, C2H2, C2H4, H2Se, H2S, PH3, COF2, CH3F, HCHO, (CH3)2O, and CH3NH2) on B12N12 and Al12N12 nanocages. Most of the studied gases are weakly (strongly) adsorbed on the B12N12 (Al12N12) nanocage. However, AsH3, H2Se, H2S, PH3, CH3F, HCHO, (CH3)2O, and CH3NH2 are strongly adsorbed on the B12N12 nanocage and H2, F2, CF4, CH4, and CF2Cl2 are weakly adsorbed on the Al12N12 nanocage. The most negative-valued molecular electrostatic potential (MESP) minimum (Vmin) corresponds to the electron-rich region (e.g., lone pair and π-bond) in the molecule. An important observation is that the adsorption energies of the gases on the B12N12 and Al12N12 nanocages are well correlated with the MESP Vmin values of the gases. Substantial changes are found in the DFT reactivity indices like chemical potential and hardness of the B12N12 and Al12N12 nanocages, mainly due to the strong gas adsorption. The quantum theory of atoms in molecules analysis suggests the covalent nature of interactions only in the AsH3/B12N12, H2Se/B12N12, H2S/B12N12, and PH3/B12N12 systems. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) Pd–In2O3/rGO aerogel was fabricated via a one-step hydrothermal treatment and freeze-drying. The morphology and structure of the 3D Pd–In2O3/rGO aerogel were examined. The aerogel material had a porous network structure, which was particularly advantageous for gas adsorption. The Pd–In2O3 nanoparticles were uniformly grown on the thin layer of rGO. The specific surface area of the aerogel and its rich pore structure inhibited aggregation and accumulation of the nanoparticles. Moreover, this structure facilitated the formation of a P–N heterogeneous structure, which ultimately enabled successful detection of hydrogen (H2) at room temperature. The sensitivity for 10 000 ppm H2 at room temperature was 27.66, and detection was stable and reproducible. Most notably, the response and recovery times for H2 were as short as 11 and 13 seconds, respectively. The addition of a hydrogen-sensitive functional material to a reduced graphene oxide aerogel shows great promise for room temperature gas sensing. [ABSTRACT FROM AUTHOR]

In this paper, the effects of five noble metal (Au, Pt, Pd, Ag, Ru)-doped MoSe2 on improving the gas sensing performance were predicted through density functional theory (DFT) based on first-principles. The adsorption of NH3, H2S, CO, C2H6O and C3H6O gas molecules on Au-, Pt-, Pd-, Ag-, and Ru-doped MoSe2 systems was investigated in terms of their stability, adsorption energy, charge transfer and density of states (DOS) and electronic structure. The results indicated that the noble metal atoms could be connected to the adjacent Se in the form of ionic bonds, which could be stably located on the surface of the MoSe2 monolayer. The adsorption distance was significantly reduced, the number of electrons transferred between the metal-doped MoSe2 substrate and the gas molecules increased, and most of the adsorption process was chemical adsorption of the noble metal-doped MoSe2 system, which suggested that the noble-metal-doped system could remarkably enhance the gas adsorption behavior compared with the intrinsic MoSe2 system. DOS analysis indicated that the noble metal-doped atoms had a great influence on the conductivity of the MoSe2 monolayer. Most notably, doping the noble metals as catalysts with high activity and stability could effectively improve the gas sensing performance, laying a solid theoretical foundation for the development of high-performance two-dimensional gas sensors based on MoSe2. [ABSTRACT FROM AUTHOR]

In this paper, the synthesis, characterization and sensing applications (in terms of liquefied petroleum gas and carbon dioxide gas) of copper antimonate (CuSb2O6) nano-polygons have been reported. The sensing surface was decorated with nano-polygons on a porous network. Structural characterization revealed the crystalline nature of CuSb2O6 with a crystallite size of 21 nm. The optical properties (UV-visible absorption and Fourier transform infrared absorption) of the annealed and as-synthesized CuSb2O6 were also studied. Further, an effort was made towards the development of an LPG sensor using the CuSb2O6 films that are characterized by high sensitivity, high stability, short response and recovery times, and most importantly, room-temperature (27 °C) operation. Examination of the gas sensing properties showed that the CuSb2O6 nano-polygons exhibited better response towards liquefied petroleum gas adsorption than carbon dioxide. The possible surface-sensing mechanism of the decorated surface on exposure to the target gas has also been discussed. The gas-sensing properties demonstrated that the CuSb2O6 nano-polygons are promising candidates for high-performance LPG sensors that operate at room temperature. [ABSTRACT FROM AUTHOR]

A cage-like MOF has demonstrated tremendous potential in gas selective adsorption and CO2 catalysis due to its distinctive structural features. Accordingly, a novel cage-like MOF 1 was synthesized using the biphenyl tricarboxylic acid ligand, (1,1′-biphenyl)-2,4,6-tricarboxylic acid (H3L), and Zn(II) via a solvothermal reaction. 1 exhibited a porous three-dimensional framework formed by interconnected dodecahedron (5.2 Å) and octahedron (4.7 Å) cages, which was based on an interesting 13-connected fcu topology. Significantly, 1a has excellent adsorption properties for C2H2 and CO2 and selective separation performance for C2H2/CO2, C2H2/CH4, and CO2/CH4. Moreover, under the action of the Lewis acid sites, 1a also shows highly efficient and recyclable catalytic properties for the reaction of CO2 with various epoxides. [ABSTRACT FROM AUTHOR]

Covalent cross-linked porous organic polymers (POPs) have shown great potential in adsorption and separation fields owing to their high surface areas, easy functionalization, and porous design using synthetic strategies. Herein, we report the facile preparation of two triphenylamine-based nitrogen-rich porous organic polyaminals (TPOAs), denoted as TPOA-F and TPOA-OH, from triphenylamine-based triazine-hexamine and commercially available fluorine- and hydroxyl-monoaldehydes, respectively via a amine–aldehyde condensation reaction without any catalyst addition. These two resulting TPOAs possessed large specific surface areas (1179 and 565 m2 g−1) and hierarchical pore distribution (0.58 to 5.20 nm). Owing to this, TPOAs exhibited highly promising application potential for natural gas purification (mainly light hydrocarbons and CO2 separation). Among them, TPOA-F shows the highest C3H8 uptake of 225 mg g−1, C2H6 uptake of 122 mg g−1, and CO2 uptake of 155 mg g−1 at 273 K/1 bar and C3H8 uptake of 187 mg g−1, C2H6 uptake of 93 mg g−1, and CO2 uptake of 95 mg g−1 at 298 K/1 bar. Then, the C3H8/CH4, C2H6/CH4, C3H8/C2H6, C3H8/CO2, C2H6/CO2, and CO2/CH4 gas mixture adsorption selectivities for TPOAs demonstrated the values of 68.7–78.8, 14.0–15.7, 4.9–5.0, 16.5–17.4, 3.4–3.5, and 4.2–4.5. Meanwhile, TPOAs also displayed considerable iodine capture performance up to 3.43 g g−1. In addition, this has surpassed many reported porous polyaminal materials for their abundant porosity and nitrogen active sites, which offer host–guest interactions due to the high electron density. This study would provide valuable guidance for the development and application of efficient POP-based adsorption and separation materials. [ABSTRACT FROM AUTHOR]

Ni-doped alumina nanoflakes are a potent sensing material for SO3 gas at 20–90 °C with moderate recovery. Herein, an economical synthesis of undoped and doped alumina for the experimental detection of SO3 target gas is reported. The Ni-doping results in an efficient fast response to all tested concentrations of the target gas and also showed good response at room temperature. However, the response increases enormously with the increase in temperature and reaches saturation at higher temperatures. Among the different temperatures, the sensor delivers a huge response at 90 °C and this temperature is optimum for sensor operation. The high Ni-doped sensor reveals an improved response of 12.40 towards 10 ppm SO3 and a response time of 9 s. The response shows a two-fold increase up to 60 ppm. The stability of the Ni-doped sensor is evaluated and validated under the ageing test over a 5 week period. Surprisingly, the sensor response shows a feeble decrease, maintaining an immense response. The sensor demonstrates ∼97% reproducibility, which assures the possibility for practical applications. Meanwhile, the Ni-dopant helps to increase oxygen adsorption and active sites. [ABSTRACT FROM AUTHOR]

Cationic exchange resins (CERs) are generally used for the purification and clarification processes of nuclear industry wastewater. The molten-salt oxidation method (MSO) can be effectively applied to the treatment of spent resins and the absorption of acid gas (such as SO2). In this study, the transformation of organic sulfur in resins in ternary molten carbonates was investigated. The FT-IR spectra proved that the existence of molten carbonates could promote the decomposition of the benzene ring, S–O and C–S bonds in the resin structure. The XRD pattern analysis revealed that organic sulfur in the sulfonic acid functional group of resins was fixed in spent salt in the form of sulfate. The XPS results showed the transformation of sulfur species into residues in the carbonate melt. The increase in temperature promoted the conversion of thiophene sulfur to sulfoxide sulfur and further to sulfones sulfur at over 550 °C in the carbonate melt. The retention rate of organic sulfur in spent salt was 82.55% at 800 °C. This study provides more theoretical guidance for the industrial treatment of spent resins and some technical support for the sustainable development of the nuclear industry. [ABSTRACT FROM AUTHOR]

A new anthracene-based metal–organic framework (MOF, named as CUST-607), [Cd3(H2O)(H3L)2(dia)2]·4DMA·10H2O (dia = 9,10-bis(1H-imidazol-1-yl)anthracene, H3L = 4,4′,4′′-[1,3,5-benzenetriyltris(carbonylimino)]tris(benzoate)), was synthesized by a solvothermal method. Through single X-ray diffraction analysis, CUST-607 displays a three-dimensional multihole network with the triclinic space group of P1¯ and (3,3,4,5)-connected nodes. Gas adsorption and desorption experiments show that CUST-607 has a microporous structure with a large surface area of 702.15 m2 g−1. CUST-607 also exhibits selective and strong adsorption of CO2 with a 40 kJ mol−1Qst value. Luminescence sensing experiments show that CUST-607 has a high selectivity for detecting nitroaromatic explosives, particularly for 2,4,6-trinitrophenol. The quenching constant Ksv is 1.43 × 105 M−1, higher than that of most reported MOFs. In addition, the CUST-607 fluorescence sensor exhibits high recyclability in detecting nitrobenzene and 2,4,6-trinitrophenol and can be used as potential sensors in practical applications. [ABSTRACT FROM AUTHOR]

In recent years, doped graphene has been often used as a gas-sensitive material, and its gas adsorption energy has received extensive attention. However, the numerous types of doped graphene make the simulation calculation study of their adsorption energy highly costly and time consuming. In this study, in order to accurately and quickly examine the CO adsorption capacity of different boron-doped graphene structures, 1864 different sets of CO adsorption energy on boron-doped graphene were obtained by simulation based on density functional theory (DFT), and an overall framework based on machine learning was then proposed. After that, three different machine learning methods were evaluated, and the random forest method was found to perform best, with the average root mean square error achieving around 0.051. This study demonstrates the power of machine learning models in uncovering complex and hidden structure–property relations in boron-doped graphene and provides the possibility of using a data-driven method for the rational design of gas-sensitive materials. [ABSTRACT FROM AUTHOR]

Two flexible ligands, 4,4′,4′′-(nitrilotris(methylene))tribenzoic acid (H3TCBA) and 1,4-bis((1H-imidazol-1-yl)methyl)benzene (BMB) have been used to construct a three-dimensional MOF with Co(NO3)2·6H2O through solvothermal techniques. The MOF is formulated as {[Co3(TCBA)2·BMB]·3DMF·8H2O}n (1). Topological analysis reveals that 1 is a 3,8-connected new net with point symbol {42·6}2{44·610·79·85}. The MOF has been characterized by single crystal X-ray diffraction, infrared spectroscopy (IR), thermogravimetry analysis (TGA), elemental analysis, UV-visible spectrum, X-ray powder diffraction (XRD), variable-temperature X-ray powder diffraction (VXRD). In addition, selective gas adsorption and magnetic properties of 1 have been explored. [ABSTRACT FROM AUTHOR]

Three lanthanum aminopolycarboxylates [La(Hida)2(H2O)2]n·nCl·4nH2O (1), K2n[La(nta)2]n·nH2O (2) and (H2en)n[La(edta)(H2O)]2n·10nH2O (3) (H2ida = iminodiacetic acid; H3nta = nitrilotriacetic acid; H4edta = ethylenediaminetetraacetic acid; en = ethylenediamine, NH2CH2CH2NH2) were isolated by gel self-assembly and were fully characterized. Structural analyses reveal that 1–3 have infinite 2D and 3D structures with different coordination modes. Topological analyses of 1–3 were also performed. Solid state 13C NMR spectra show that the coordinated β-CO2 groups give obvious downfield shifts compared with free β-CO2 groups. Interestingly, 3 possesses 5.8 Å diameter tunnels inside the crystals, which can selectively adsorb very small amounts of O2 at 5.49 mg g−1 and 29.9 bar, while no adsorption of H2, N2, CH4 and CO2 is observed. Compared with lanthanum 1,3-propylenediaminetetraacetate {La(H2O)4[La(1,3-pdta)(H2O)]3}n·11.25nH2O (4) with 10.0 Å diameter tunnels, the latter can adsorb CO2, O2 and N2 at 55.33, 18.01 and 4.41 mg g−1 and 29.9 bar, respectively. This shows that smaller diameter tunnels have better selectivity towards the adsorption of specific gases. When the diameter of the tunnels increases, the adsorption amounts of numerous gases increase significantly with a decrease in selectivity. [ABSTRACT FROM AUTHOR]

Three new carbazole containing cross-linked polymers namely AH-Poly, TM-PDA-Poly and TMB-PDA-Poly were designed and successfully synthesized by an oxidative polymerization protocol. The prepared AH-Poly showed a specific BET surface area of 822 m2 g−1 and 10.6 wt% CO2 gas adsorption at 273 K. Moreover, two imide linked PDA-polymers exhibited a significantly excellent specific surface area of 1459–1691 m2 g−1 and possess excellent CO2 adsorption capacity of 19 wt% and 12 wt% at 273 K and 295 K, respectively. This work proposed that the design of monomer with carbazole as the network core, imide bonds and heteroatom enrichment promotes the fabrication of very stable and highly efficient microporous polymers with high CO2 absorption capacities. [ABSTRACT FROM AUTHOR]

The gas adsorption properties and NH3-SCR reaction mechanism over the Fe2O3/Ni(111) surface were investigated by a DFT-D study. The results show that the Fe2O3 cluster has more excellent gas adsorption performance than the Ni carrier. Single gas adsorption products are coordinated ammonia, nitroso, and adsorption oxygen, respectively. The presence of O2 promotes bimolecular adsorption. Three NH3-SCR reaction routes are revealed and mainly follow the Eley–Rideal mechanism. The reaction of NH3 and NO involves five steps: (1) NH3* dehydrogenation, (2) NH2NO* generation, (3) NHNO* generation, (4) NHNO* dissociation, and (5) H2O generation. NHNO* dissociation into N2 releases lots of energy. The reaction of O2 and NO eventually forms NO2, and is an energetically favorable process. Reaction of NO2 with NH3 involves three steps: (1) NH2NO2 generation, (2) NHNO2 generation, and (3) NHNO2 dissociation. NHNO2* decomposition and H2O* desorption as the rate-determining steps control the whole reaction rate. In addition, the reason for the high NOx conversion of "fast-SCR" is that NO2 reacts more easily with NH2 to form a nitrogen intermediate compared to NO. [ABSTRACT FROM AUTHOR]

In this manuscript, we describe the construction and self-assembly studies of a series of metal-directed coordination polymers using a combination of dicarboxylic acid, 5-azido isophthalic acid (N3-IPA) and bipyridine, 1,2-bis(4-pyridyl)-ethane (BPE) mixed-ligand systems. The combination of a rigid acid and a flexible bipyridyl ligand serves the purpose of generating diverse architectures with different metal centres ranging from two-dimensional grids and complex three-dimensional frameworks. The ligand molecules exhibited variable conformations as well as variable coordination behaviours when different metal ions were used. We report herein, the synthesis and structural aspects of seven metal-directed MOFs,{[Cu(μ-N3-IPA)(μ-BPE)]·(DMF)0.5}n (1), [Co(μ-N3-IPA)(μ-BPE)1.5]n (2), [Ni(μ-N3-IPA)(μ-BPE)1.5]n (3), [Cd(μ-N3-IPA) (N3-HIPA) (μ-BPE)]n (4), {[Mn(μ-N3-IPA)(μ-BPE)1.5]·(DMF)(H2O)}n (5), {[Zn(μ-N3-IPA)(μ-BPE)]·[(H2O)](CH3OH)}n (6), [Zn(μ-N3-IPA)(μ-BPE)]n (7). Compounds 1 and 3 showed interesting structures, wherein the immobilized nitrogen-rich azide groups are situated in the inner surfaces of the walls that encompass a columnar pore, which represents a highly favourable situation for the CO2 gas adsorption. Both compounds showed the selective uptake of CO2 gas compared to N2 gas. The cobalt-based compound 2 showed an impressive photocatalytic degradation of toxic dye molecules with a potential application in environmental remediation. The copper-based compound 1, on the other hand, exhibited a nice example of a heterogeneous catalytic reduction of 4-nitrophenol to 4-aminophenol. [ABSTRACT FROM AUTHOR]

Herein, we investigated the effects of hydrogen bond acceptors on the surface of two-dimensional (2D) polyimide (PI) towards NH3, H2S, CO, H2, CH4, NO, NO2, C6H6 and C3H6O gas molecules through first-principles calculations based on density functional theory (DFT). The most stable adsorption configurations are proposed by simulating the adsorption behavior of gas molecules at three 2D PI positions (1-2DPI, 2-2DPI, and 3-2DPI) with different numbers of hydrogen bonds, and the parameters including adsorption energy, charge transfer, electron density, density of states (DOS), recovery time and frontier molecular orbitals were calculated. The simulation results indicate that the absolute values of adsorption energy of 2DPI-NH3, 2DPI-H2S and 2DPI-CO configurations are greater than 0.8 eV, which can be regarded as chemisorption, while those of the 2DPI-H2, 2DPI-CH4, 2DPI-NO, 2DPI-NO2, 2DPI-C6H6 and 2DPI-C3H6O are all less than 0.6 eV, which can be considered as physisorption. Interestingly, the existence of intermolecular hydrogen bonds significantly improves the adsorption capacity of 1-2DPI and 2-2DPI systems compared with the 3-2DPI system. Moreover, the DOS diagram demonstrates that these gas molecules exhibit a different influence on the electronic properties of the 2DPI substrate. It is worth noting that the electronic properties of 2DPI can be effectively changed after the adsorption of NH3, H2S and CO, and 2-2DPI is the best position for gas adsorption. Our results indicate that the 2DPI monolayer with 2D structure and hydrogen bonds may be a good candidate for the detection of NH3, H2S and CO, which opens up new prospects to design and research gas sensor applications. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) flower-like zinc and aluminum-sodium dodecyl sulfate-layered double hydroxides (ZnAl-SDS-LDHs) intercalated by anions were prepared using a simple one-step hydrothermal method. Making use of urea as a precipitant and SDS as a template agent affords samples with intriguing ultra-thin nanosheets. Amongst them, the sample ZAS-2, synthesized with the Zn : Al molar ratio of 2 : 1, possessed nanosheets only 3.2 nm thick, with an average pore diameter of 3–12 nm, and a large specific surface area of 85.5 m2 g−1. At room temperature (25 °C) and a relative humidity of 26%, ZAS-2 exhibited a very rapid response/recovery time and 28.6 response to 100 ppm NO2. Its fabricated sensor was endowed with good selectivity, high stability and low detection limit. The outstanding activity was mainly attributed to the unique microstructure of newly-synthesized ZAS materials that are composed of ultra-thin nanosheets along with plenty of embedded pores, and to the increased large specific surface area; all together promoting gas diffusion and adsorption. In addition, the coupling effect between hydroxyls and hydrogens of water adsorbed on the surface of LDH laminates further provides a static channel for efficient and fast carrier transport. Therefore, the heterostructure constructed by Zn(OH)2 and Al(OH)3 was beneficial for gas sensing performance. [ABSTRACT FROM AUTHOR]

Based on density functional theory (DFT) calculations, the adsorption geometries, stability and catalytic properties of single-atom Ru and Mo anchored on graphenylene sheets (gra-Ru and gra-Mo) are comparatively investigated. Compared with isolated gas molecules, different kinds of coadsorbed gas reactants (2NO, 2CO, CO–O2 and NO–O2) exhibit high stability on gra-Ru and gra-Mo sheets, and the coadsorbed configurations of gas reactants are considered as initial states for the NO and CO oxidation reactions. According to the calculated energy barriers, NO oxidation reactions on the gra-Ru sheet through the Langmuir–Hinshelwood (LH) mechanism have relatively large energy barriers than CO oxidation reactions. In addition, the preadsorbed 2NO reacting with 2CO (2NO + 2CO → 2CO2 + N2) on gra-Ru and gra-Mo sheets through the Eley–Rideal (ER) mechanism (<0.5 eV) are energetically more favorable reactions. Therefore, different kinds and adsorption geometries of gas reactants have a close relationship with the reaction mechanism and energy barriers for the NO and CO oxidation, which provide an important reference for designing novel graphenylene-based catalysts for the removal of toxic gases. [ABSTRACT FROM AUTHOR]

Two new metal–organic frameworks (MOFs), [Zn2(μ3-OH)(dia)(btb)·2H2O]·EtOH·0.5DMF (1) and [Cd2Na(btb)2(dia)2]·2DMF·H2O (2) (dia = 9,10-bis(1H-imidazol-1-yl)anthracene, btb = 1,3,5-tris(4-carboxyphenyl)benzene), have been synthesized under solvothermal conditions. Compound 1 exhibits a (3,10)-connected net based on {Zn4} SBUs and compound 2 presents a (3,8)-connected network with a [Cd2Na] unit. The results show that both 1 and 2 have a microporous structure and selective adsorption capacity for CO2, and the Qst value is 36 kJ mol−1 and 35 kJ mol−1, respectively. Studies on luminescence sensing show that 1 and 2 are highly selective and recyclable in the detection of nitroaromatic explosives, especially for TNP. It is noteworthy that the quenching constant Ksv of 1 and 2 for TNP (2.84 × 105 M−1 and 2.50 × 105 M−1) is higher than that of most reported compounds. [ABSTRACT FROM AUTHOR]

Mercury has been the focus of environmental concern and scientific research for decades due to the risks associated with its use, release and emission. An international agreement established in 2017 during the UN Minamata Convention highlighted the need for innovative approaches and technology to tackle these problems. The use of regenerable sorbents for mercury removal in the gas phase is a possible solution that can avoid the generation of new mercury-contaminated waste. However, to make significant progress in this field, it is necessary to develop efficient, economic and environmentally friendly sorbents, for which, a good understanding of the mechanism of adsorption in this type of process is needed. In this study, several kinetic models were applied to determine the rate-controlling step in the adsorption process of elemental mercury by regenerable sorbents based on gold. Three diffusional models (Weber and Morris, Bangham and pseudo-first order models) and two adsorptive models (pseudo-second order and Elovich models) were tested. The results of this study show that external diffusion from the gaseous phase to the sorbent particles is the rate-limiting step. The complexity of the process is also reflected in the results obtained, which indicate that pore diffusion plays a significant role over most of the mass transfer zone, while adsorption itself becomes determinant only when the saturation of the sorbent is near. [ABSTRACT FROM AUTHOR]

The adsorption of environmental gas molecules, i.e., NH3, NO, and NO2 on the γ-PC surface has been studied using first-principles calculations. The lowest-energy configurations of these molecules on the γ-PC surface were found and the adsorption energies were calculated. The NH3, NO, and NO2 molecules were found to be physisorbed on the γ-PC surface. The analysis of the charge transfer between the molecules and the surface predicted NH3 and NO as donors to γ-PC, while NO2 acted as an acceptor to γ-PC. Remarkable changes in the band structure of γ-PC were found upon the adsorption of NO2 on its surface. In addition, significant modulations in the work function of γ-PC were observed after the adsorption of NH3 and NO. [ABSTRACT FROM AUTHOR]

Covalent organic triazine frameworks (CTFs) are a subclass of covalent organic frameworks and conjugated microporous polymers that exhibit heteroatom effects and possess high surface areas and excellent chemical and thermal stabilities; they have applications in energy storage and gas adsorption. In this study, we prepared two microporous polymers the pyrene-functionalized CTFs Pyrene-CTF-10 and Pyrene-CTF-20—through ionothermal treatment of 1,3,6,8-cyanopyrene (TCNPy) in the presence of molten zinc chloride (ZnCl2) at 500 °C (at ZnCl2-to-TCNPy molar ratios of 10 : 1 and 20 : 1, respectively). Pyrene-CTF-10 and Pyrene-CTF-20 had specific BET surface areas of 819 and 1019 m2 g−1, respectively, with pore size distributions of 1.10 and 1.35 nm, respectively, and high char yields (up to 70%). Furthermore, these Pyrene-CTF polymeric frameworks exhibited excellent specific capacitances at a current density of 0.5 A g−1: 380 F g−1 for Pyrene-CTF-10 and 500 F g−1 for Pyrene-CTF-20. In addition, both Pyrene-CTFs had excellent cycling stability, retaining 97% of their capacitances after cycling 2000 times at a current density of 10 A g−1. Moreover, Pyrene-CTF-10 displayed good CO2 uptake capacity (2.82 and 5.10 mmol g−1 at 298 and 273 K, respectively). [ABSTRACT FROM AUTHOR]

In this study, superamphiphobic coatings, which could repel liquids with a surface tension as low as 21.6 mN m−1 (n-octane), were prepared using a spray-coating method based on a flower-like hierarchical structure and highly fluorinated TiO2/SiO2 composite particles. And the coating exhibited broad liquid repellency to water-based composites, various oils, organic solvents and hot water. Moreover, the coating also possessed remarkable mechanical and chemical stability towards various forms of mechanical damage and in harsh chemical environments. Multiple features enable the coating to find more vital applications in antifouling, corrosion resistant, fuel transportation, gas adsorption, and protective coatings, etc. [ABSTRACT FROM AUTHOR]

The solubility of methane (CH4) in ionic liquids (ILs) is required in order to develop processes involving CH4, such as methane conversion and CO2/CH4 separation from natural gas or biogas processes. Nevertheless, the solubility of CH4 in ILs is still very rarely achieved and, consequently, fundamental knowledge about the factors that govern the solubility are still poorly understood. Therefore, this work aims to extend the solubility data of CH4 in various ILs and to gain some insights into the factors at a molecular level that play a role in the solubility process through experimental and computational modelling using Conductor-like Screening Model for Real Solvent (COSMO-RS). The solubility of CH4 in 17 commercial ILs was measured experimentally at four different temperatures (298.15 to 343.15 K) and pressures up to 8 MPa. The large number of ILs studied allows the study of the impact of the cation and anion head group and the alkyl chain length on the solubility of CH4. From the experimental solubility data collected, Henry's law constant (KH) values were calculated. The results show that the solubility of CH4 increases with decreasing temperature and increasing pressure. The solubility of CH4 can also be enhanced by increasing the alkyl chain length of the IL cation or anion. Despite the inability of COSMO-RS to make quantitative predictions, the model is able to predict accurately the impact of the IL cation head group, anion, and alkyl chain length on the solubility of CH4. Good correlation between the electrostatic – misfit energy, HE,MF, of CH4 and the experimentally calculated KH values was obtained (R2 = 0.932). This correlation indicates, for the first time, that the electrostatic – misfit energy arising from the repulsive interaction of CH4 plays a dominant role in determining its solubility in ILs. In addition, it is shown that the IL size and van der Waals forces only have marginal influences on the solubility of CH4. The experimental and computational modelling results in this work could pave the way to designing ILs as a medium for gas absorption and separation involving CH4. [ABSTRACT FROM AUTHOR]

The capability of pristine and M-doped (M = Ti, Cr, Fe, Ni and Zn) gallium nitride nanosheets (M-GaNNS) was explored at the Grimme-corrected PBE/double numerical plus polarization (DNP) level of theory for adsorbing and sensing of the carbon monoxide (CO) molecule. It was found that the binding energies for MGaGaNNS were greater than for MNGaNNS, indicating that Ga sites are more energetically favorable than N sites for M doping. The results demonstrated that the decrease of the energy gap for FeGa,N-GaNNS and ZnGa-GaNNS was greater than the others. Besides, M doping of GaNNS increased the adsorption energies of CO toxic gas in comparison with pristine GaNNS. The energies of adsorption were calculated to be in the range of −0.03 (TiGa-GaNNS) to −2.55 (FeN-GaNNS) eV. In addition, adsorption of CO gas decreased the energy gap of the GaNNS and the order was Eg (MNGaNNS) > Eg (MGaGaNNS). Due to the changes in the energy gaps of the GaNNS upon adsorption of CO, it was predicted that CrGaGaNNS and FeNGaNNS could be suitable for sensing of CO gas. Based on the obtained results, it is predicted that FeNGaNNS could be a good candidate for sensing and removing the toxic air pollutant CO gas. [ABSTRACT FROM AUTHOR]

A series of BODIPY-containing microporous organic polymers was synthesized via a Sonogashira–Hagihara cross-coupling reaction of a BODIPY derivative with triple polymerisable groups and a range of aryl–alkyne monomers. All of the polymers show high isosteric heats of CO2 adsorption (23.3–27.3 kJ mol−1) because the incorporation of heteroatoms (N, B, F) from the BODIPY unit into the polymer skeleton enhanced the binding affinity between the pore wall and CO2 molecules. The aryl–alkyne monomer has a large influence on the surface area and CO2 adsorption performance of the resulting polymers. The polymer BDPCMP-3 shows a high Brunauer–Emmett–Teller specific surface area of up to 725 m2 g−1, while BDPCMP-2 with a low surface area of 582 m2 g−1 shows a high CO2 uptake ability of 2.25 mmol g−1 at 1.13 bar/273 K with a CO2/N2 adsorption selectivity of 32.3. [ABSTRACT FROM AUTHOR]

Achieving a cost-effective preparation of 3D porphyrin-based microporous organic polymers (PMOPs) for the adsorption and separation of carbon dioxide (CO2), ethane (C2H6), and methane (CH4) remains difficult. In this study, two 3D PMOP networks that originated from triphenylphosphine and tetraphenylsilane units for CO2, C2H6, and CH4 adsorption/separation, PMOP-P and PMOP-Si, were successfully fabricated by a facile one-pot method using tri(4-formylphenyl)phosphine (TFPP) and tetrakis(4-aldehydephenyl)silane (TFPSi) with inexpensive pyrrole, respectively. The as-prepared PMOPs consisted of roughly spherical particles with specific surface areas between 645 and 814 m2 g−1 and pore sizes smaller than 2 nm. In addition, the PMOPs showed medium CO2, C2H6, and CH4 gas adsorption performances. Compared with PMOP-P, PMOP-Si the tetraphenylsilane moiety displayed higher microporosity. It also exhibited CO2, C2H6, and CH4 gas uptakes of up to 138.9, 71.0, and 14.7 mg g−1, respectively, at 273 K and 1 bar. The 138.9 mg g−1 CO2 uptake exceeded those of previously reported PMOP materials. Moreover, the as-prepared PMOP-P containing triphenylphosphine units possessed a smaller pore size than PMOP-Si and exhibited C2H6/CH4 and CO2/CH4 selectivities as high as 24.3 and 10.9 at 273 K, respectively, derived from the initial slope method. The results are helpful for the future design and construction of microporous organic polymers originating from triphenylphosphine and tetraphenylsilane units for simple gas adsorption and separation. [ABSTRACT FROM AUTHOR]

Bimetallic metal–organic frameworks (MOFs) possess two different metal ions as nodes in their molecular frameworks. They are prepared by either one-pot syntheses, wherein different metals are mixed with suitable ligands and linkers, or by adopting post-synthetic modifications by soaking a monometallic MOF in a concentrated solution of a different (but compatible) metal ion. These bimetallic MOFs exhibit synergistic effects and enhanced properties compared to their monometallic counterparts, such as improved adsorption selectivity, selective catalysis and structural stability. Certainly, there are still many open challenges, given that bimetallic MOFs suffer from the typical drawbacks of MOFs, including high moisture sensitivity, easy oxidation due to their varying oxidation states, and possible metal leaching in liquids. In the present perspective, progress in the research on the synthesis and properties of bimetallic MOFs has been reviewed systematically, describing the synthetic strategies adopted to prepare targeted bimetallic MOFs and their applications in gas adsorption, catalysis, energy storage and conversion, and luminescence sensing. Additionally, the challenges facing the synthesis of stable and robust bimetallic MOFs have been discussed with a final outlook on their further development prospects. [ABSTRACT FROM AUTHOR]

A porous metal–organic framework, {[Zn(BDC)1/2(trz)]·DMAC}n (Zn-BDC), was synthesized hydrothermally with the decomposition of 2,3-di(1,2,4-triazole)quinoxaline ligand (H2BDC = 1,4-benzenedicarboxylic acid; Htrz = 1,2,4-1H-triazole). Structural analysis indicates the porosity of Zn-BDC with distorted oblong cages. Gas adsorption studies of N2 and Ar on activated Zn-BDC reveal the BET surface areas of 587.3 and 519.5 m2 g−1, respectively. Considering the certain size of the cages, Zn-BDC can separate organic compounds with different sizes through a MOF-column chromatographic method and deliver 5-fluorouracil, which can act as an anticancer drug. Zn-BDC has also been employed as a support for Pd nanoparticles. The results of catalytic hydrogenation of 4-nitrophenol demonstrate that the catalytic activity of Pd@Zn-BDC is superior enough compared to most Pd catalysts reported. [ABSTRACT FROM AUTHOR]

In this work, we study the adsorption properties of N2, H2, O2, NO, NO2, CO, CO2, and SO2 on a Sc2CO2 monolayer based on first-principles calculations from density functional theory. The structural properties of the Sc2CO2 monolayer after adsorption of various gases have been elucidated. The preferred adsorption sites for each gas are determined. It has been established that the CO2, CO, H2 and N2 molecules are physically adsorbed on the Sc2CO2 monolayer, while the NO, SO2, NO2, and O2 molecules are chemically adsorbed on the Sc2CO2 monolayer. The chemical adsorption of O2 molecules, which are a fundamental component of air, significantly changes the electronic properties of the Sc2CO2 monolayer. This fact limits the prospect of application of the Sc2CO2 monolayer in gas sensors or capture of toxic gases such as SO2 and NO. [ABSTRACT FROM AUTHOR]

A series of isoreticular MOFs (1–4) with rare lon topologies have been rationally synthesized using the ligand benzotriazole-5-carboxylic acid and auxiliary aromatic dicarboxylic ligands based on novel double secondary building units (SBUs) and trigonal-prism building units. On the other hand, MOFs 1–4 all adopt pillared-layer structures based on the same honeycomb layers, and then the neighboring layers are linked together through the ditopic carboxylate pillars. They all exhibit similar constructions but different pore characteristics (volumes and surfaces), owing to convertible ditopic ligands pillaring the same layers. Notably, they all possess a certain degree of air and water stability and CO2 uptake capacity. In addition, we researched the luminescence properties of MOFs 1–4. We found that MOF 2 can be used as a fluorescent probe for exhibiting a clear fluorescent enhancement “turn on” response for H2O and a fluorescence quenching “turn-off” response for nitrobenzene (NB). [ABSTRACT FROM AUTHOR]

A glucose-based nanoporous organic polymer (glu-NOP) was designed and synthesized facilely by a Scholl coupling reaction using benzylated glucose as a single monomer. The glu-NOP exhibits a high surface area (682 m2 g−1), large pore volume, and high thermal stability, making it an efficient adsorbent for CO2 capture (2.84 mmol g−1 at 1.0 bar/273 K) and separation. In addition to its capabilities for gas sorption, the highly biocompatible glu-NOP was also evaluated as a drug carrier for the delivery of a hydrophobic drug, ibuprofen (IBU) and a hydrophilic drug, 5-fluorouracil (5-FU). The solution impregnation method was used for drug loading and the drug release kinetics were determined by UV spectroscopy. The results presented here reveal that, for IBU/glu-NOP and 5-FU/glu-NOP complexes, the drug loading efficiency is about 10.7 wt% and 30 wt%, respectively. More importantly, very slow delivery of IBU was achieved under physiological conditions, which is even better than that of its analogue MIL-53(Cr, Fe). This could effectively avoid frequent and invasive dosing and improve patient compliance. This study, therefore, supports the potential of glu-NOP as a simple and stable platform for both gas uptake and drug delivery. [ABSTRACT FROM AUTHOR]

Mesoporous In2O3 nanocrystals (INS) were successfully prepared using SBA-16 as the template. The sample INS-3, synthesized from a 0.3 M In(NO3)3 solution, had a 7.27 nm mean pore size and 82.32 m2 g−1 specific surface area. The mesoporous In2O3 nanocrystals were interconnected In2O3 small grains (∼5 nm) with a pore wall thickness of about 5–10 nm, and the natural pores provided effective gas adsorption–desorption and fast transportation of carriers, resulting in better diffusivity of the analyte gases. Therefore, the INS-3 sensor exhibited sensing properties with a high response of 158.7 and a low detection limit of 970 ppb to 97 ppm NOx at room temperature (RT), which can be attributed to the synergistic effect between its unique mesoporous and well-crystalline structure. The INS-3 sensor has significant applications for gas sensing. [ABSTRACT FROM AUTHOR]