FT-IR study on CO<Subscript>2</Subscript> adsorbed species of CO<Subscript>2</Subscript> sorbents

The stability of amine-functionalized silica sorbents prepared through the incipient wetness technique with primary, secondary, and tertiary amino organosilanes was investigated. The prepared sorbents were exposed to different gaseous streams including CO₂/N₂, dry CO₂/air with varying concentration, and humid CO₂/air mixtures to demonstrate the effect of the gas conditions on the CO₂ adsorption capacity and the stability of the different amine structures. The primary and secondary amine-functionalized adsorbents exhibited CO₂ sorption capacity, while tertiary amine adsorbent hardly adsorbed any CO₂. The secondary amine adsorbent showed better stability than the primary amine sorbent in all the gas conditions, especially dry conditions. Deactivation species were evaluated using FT-IR spectra, and the presence of urea was confirmed to be the main deactivation product of the primary amine adsorbent under dry condition. Furthermore, it was found that the CO₂ concentration can affect the CO₂ sorption capacity as well as the extent of degradation of sorbents.     

Effect of amine double-functionalization on CO<Subscript>2</Subscript> adsorption behaviors of silica gel-supported adsorbents

Amine double-functionalized adsorbents were fabricated using silica gel as supports and their capabilities for CO₂ capture were examined. Aminopropyltrimethoxysilane (1N-APS), and N¹-(3-trimethoxysilylpropyl)diethylenetriamine (3N-APS) were used as grafted amine compounds, and tetraethylenepentamine and polyethyleneimine were used as impregnated species. The influence of double-functionalization method on the CO₂ adsorption performance and textural properties of adsorbents was investigated. The adsorption capacity, the amine efficiency, and the thermal stability of double-functionalized sorbents depend strongly upon molecular variables associated with two different functional states (i.e., chemically grafted and physically impregnated amines). The temperature dependence of adsorption isotherms reveals that the CO₂ adsorption behavior in the double-functionalized adsorbents follow the diffusion limitation model proposed by Xu et al. (Energy Fuels 16:1463–1469, 2002) where the CO₂ adsorption is helped by the diffusion of impregnated amines. It is also found that the adsorption isotherm in the double-functionalized sorbent system with a proper choice for grafted and impregnated amines is nearly independent of temperature, which may offer a novel means to fabricate practically useful sorbents that can be used in a wide range of temperature without loss of CO₂ adsorption capacity.     

A Novel Synthesis of the Macrocyclic Spermidine Alkaloid (+)‐(S)‐Dihydroperiphylline

A novel, short, and highly stereoselective synthesis of the macrocyclic spermidine alkaloid (+)‐(S)‐dihydroperiphylline ( 15 ) is described. The key synthetic steps were the stereoselective addition of the chiral amine 1 to the cinnamate 2 and cyclization of the bis[toluene‐4‐sulfonamide] precursor 12 in the presence of Cs₂CO₃ as a template. Unambiguous assignments of the signals in both the ¹H‐ and ¹³C‐NMR spectra of 15 were achieved by 2D NMR spectra.     

Effect of various aminosilanes functionalized inside nanoporous silica on CO<Subscript>2</Subscript> adsorption performance

Three different aminosilanes ((3-aminopropyl)trimethoxysilane (1NS), N-[3-(trimethoxysilyl) propyl]ethylenediamine (2NS), N¹-(3-trimethoxysilylpropyl)diethylenetriamine (3NS)) were grafted covalently inside nanoporous silica (NPS-1) with a large surface area to prepare CO₂ adsorbents. The prepared CO₂ sorbents were evaluated for their CO₂ sorption capacity, kinetic behavior, temperature programmed desorption (TPD) and textural properties. Grafting efficiency of 1NS was better due to the smaller molecular size compared to 2NS and 3NS, which are difficult to react with the hydroxyl group of the silica surface due to steric hindrance. The highest adsorption capacity of 7.0 wt% was observed for the 2NS/NPS-1 adsorbent, followed by 5.2 wt% for 1NS/NPS-1, then 5.0 wt% for 3NS/NPS-1. The adsorption capacity of 2NS/NPS-1 was highest at 30 °C, and it gradually decreased as the adsorption temperature increased. TPD analysis showed that the reaction of primary amine of 2NS with CO₂ inside the nanoporous silica could form less thermally stable carbamic acid and carbamate compared to 1NS and 3NS.     

Enhanced CO2 Adsorption over Polymeric Amines Supported on Heteroatom‐Incorporated SBA‐15 Silica: Impact of Heteroatom Type and Loading on Sorbent Structure and Adsorption Performance

Silica supported amine materials are promising compositions that can be used to effectively remove CO₂ from large stationary sources, such as flue gas generated from coal‐fired power plants (ca. 10 % CO₂) and potentially from ambient air (ca. 400 ppm CO₂). The CO₂ adsorption characteristics of prototypical poly(ethyleneimine)–silica composite adsorbents can be significantly enhanced by altering the acid/base properties of the silica support by heteroatom incorporation into the silica matrix. In this study, an array of poly(ethyleneimine)‐impregnated mesoporous silica SBA‐15 materials containing heteroatoms (Al, Ti, Zr, and Ce) in their silica matrices are prepared and examined in adsorption experiments under conditions simulating flue gas (10 % CO₂ in Ar) and ambient air (400 ppm CO₂ in Ar) to assess the effects of heteroatom incorporation on the CO₂ adsorption properties. The structure of the composite adsorbents, including local information concerning the state of the incorporated heteroatoms and the overall surface properties of the silicate supports, are investigated in detail to draw a relationship between the adsorbent structure and CO₂ adsorption/desorption performance. The CO₂ adsorption/desorption kinetics are assessed by thermogravimetric analysis and in situ FT‐IR measurements. These combined results, coupled with data on adsorbent regenerability, demonstrate a stabilizing effect of the heteroatoms on the poly(ethyleneimine), enhancing adsorbent capacity, adsorption kinetics, regenerability, and stability of the supported aminopolymers over continued cycling. It is suggested that the CO₂ adsorption performance of silica–aminopolymer composites may be further enhanced in the future by more precisely tuning the acid/base properties of the support.     

Synthesis of amine-modified mesoporous materials for CO2 capture by a one-pot template-free method

A one-pot template-free route was developed for the synthesis of novel tetraethylenepentamine modified porous silica as CO₂ adsorbents, the obtained materials were characterized by N₂ adsorption/desorption, thermogravimetry, elemental analysis, Fourier transform infrared spectrometry,scanning electron microscopy and transmission electron microscopy. It was found that the amine species were inserted into the silica skeleton, which considerably enhanced their dispersion. Compared with similar materials derived from impregnation, the porous structure of the silica can be better reserved, leading to a promising CO₂ adsorption capacity of 3.98 mmol CO₂/g-adsorbent and a fast adsorption kinetic in simulated flue gas at 348 K. The resulted adsorbents could also be easily regenerated and showed a good durability in multiple adsorption–desorption cycles. All these features make this method a promising option for the preparation of CO₂ adsorbents.     

Solid Amine Adsorbent Prepared by Molecular Imprinting and Its Carbon Dioxide Adsorption Properties

A carbon dioxide imprinted solid amine adsorbent (IPEIA‐R) with polyethylenimine (PEI) as a skeleton was conveniently prepared by using glutaraldehyde to cross‐link carbon dioxide‐preadsorbed PEI. As confirmed by FTIR, FT‐Raman, and ¹³C NMR spectroscopy, CO₂ preadsorbed on PEI could occupy the reactive sites of amino groups and act as a template for imprinting in the cross‐linking process. The imino groups formed from the cross‐linking reaction between glutaraldehyde and PEI could be reduced by NaBH₄ to form CO₂‐adsorbable amino groups. The adsorption results indicated that CO₂ imprinting and reduction of imino groups by NaBH₄ endowed the adsorbent with a higher CO₂ adsorption capacity. Compared with PEI‐supported mesoporous adsorbents, the solid amine adsorbent with PEI as a skeleton can avoid serious pore blockage and CO₂ diffusion resistance, even with a high amine content. The solid amine adsorbent with PEI as a skeleton showed a remarkable CO₂ adsorption capacity (8.56 mmol g^?1) in the presence of water at 25 °C, owing to the high amine content and good swelling properties. It also showed promising regeneration performance and could maintain almost the same CO₂ adsorption capacity after 15 adsorption–desorption cycles.     

Influence of the Solvent Properties on MCM-41 Surface Modification of Aminosilanes

Novel CO₂ adsorbents were prepared by grafting aminosilanes on mesoporous silica MCM-41. The effects of solvent and temperature on the grafting of the amine group were studied. The results of thermal gravimetric analysis of the AEAPDMS-MCM-41s produced in different solvents revealed that the nonpolar solvent toluene and the aprotic polar solvent THF are beneficial to the amine group modification reaction. The CO₂ adsorption capacity of AEAPDMS-MCM-41s produced in toluene had a relatively high value of 2.20 mmol⋅g⁻¹.     

Insights into the Oxidative Degradation Mechanism of Solid Amine Sorbents for CO2 Capture from Air: Roles of Atmospheric Water

Direct air capture (DAC) processes for extraction of CO₂ from ambient air are unique among chemical processes in that they operate outdoors with minimal feed pretreatments. Here, the impact of humidity on the oxidative degradation of a prototypical solid supported amine sorbent, poly(ethylenimine) (PEI) supported on Al₂O₃, is explored in detail. By combining CO₂ adsorption measurements, oxidative degradation rates, elemental analyses, solid-state NMR and in situ IR spectroscopic analysis in conjunction with ¹⁸O labeling of water, a comprehensive picture of sorbent oxidation is achieved under accelerated conditions. We demonstrated that the presence of water vapor can play an important role in accelerating the degradation reactions. From the study we inferred the identity and kinetics of formation of the major oxidative products, and the role(s) of humidity. Our data are consistent with a radical mediated autooxidative degradation mechanism.     

Adsorption and Purification of Baicalin from Scutellaria baicalensis Georgi Extract by Ionic Liquids (ILs) Grafted Silica

Baicalin which has multiple biological activities is the main active component of the root of Scutellaria baicalensis Georgi (SBG). Although its isolation and purification by adsorption methods have aroused much interest of the scientific community, it suffered from the poor selectivity of the adsorbents. In this work, an environmentally benign method was developed to prepare ionic liquids (ILs) grafted silica by using IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₄mim]NTf₂) and ethanol as reaction media. The IL 1-propyl-3-methylimidazolium chloride ([C₃mim]Cl) grafted silica ([C₃mim]⁺Cl⁻@SiO₂) was used to adsorb and purify baicalin from the root extract of Scutellaria baicalensis Georgi (SBG). Experimental results indicated that the adsorption equilibrium can be quickly achieved (within 10 min). The adsorption behavior of [C₃mim]⁺Cl⁻@SiO₂ for baicalin was in good agreement with Langmuir and Freundlich models and the adsorption was a physisorption process as suggested by Dubinin–Radushkevich model. Compared with commercial resins, [C₃mim]⁺Cl⁻@SiO₂ showed the strongest adsorption ability and highest selectivity. After desorption and crystallization, a purity of baicalin as high as 96.5% could be obtained. These results indicated that the ILs grafted silica materials were promising adsorbents for the adsorption and purification of baicalin and showed huge potential in the purification of other bioactive compounds from natural sources.     

Direct Air Capture of CO2 by Physisorbent Materials

Sequestration of CO₂, either from gas mixtures or directly from air (direct air capture, DAC), could mitigate carbon emissions. Here five materials are investigated for their ability to adsorb CO₂ directly from air and other gas mixtures. The sorbents studied are benchmark materials that encompass four types of porous material, one chemisorbent, TEPA‐SBA‐15 (amine‐modified mesoporous silica) and four physisorbents: Zeolite 13X (inorganic); HKUST‐1 and Mg‐MOF‐74/Mg‐dobdc (metal–organic frameworks, MOFs); SIFSIX‐3‐Ni , (hybrid ultramicroporous material). Temperature‐programmed desorption (TPD) experiments afforded information about the contents of each sorbent under equilibrium conditions and their ease of recycling. Accelerated stability tests addressed projected shelf‐life of the five sorbents. The four physisorbents were found to be capable of carbon capture from CO₂‐rich gas mixtures, but competition and reaction with atmospheric moisture significantly reduced their DAC performance.     

Immobilized copper catalyst for atom transfer radical addition and polymerization

A novel multidentate amine grafted on silica gel and magnetic microsphere was prepared. Its chemical structure was confirmed by C¹³ NMR, XPS and FTIR, and the nitrogen content was determined by elemental analysis. It was also used as a ligand for CuCl and successfully catalyzed the atom transfer radical addition of both carbon tetrachloride (CCl₄) to methyl methacrylate and methyl trichloroacetate to styrene, repeatedly. The conversion and purity of the product were determined through gas chromatography and ¹H NMR, respectively. The immobilized copper catalyst complex was also used in atom transfer radical polymerization of styrene initiated by 1,1,1,3‐tetrachloro‐3‐phenylpropane and methyl methacrylate initiated by methyl 2‐methyl‐2,4,4,4‐tetrachlorobutyrate, respectively. Although the polymerization took place successfully, it did not proceed in a controlled fashion. Copyright © 2010 John Wiley & Sons, Ltd.     

Au/α-Fe2O3 催化剂存贮失活环境因素及机理分析

 采用沉积沉淀法制备了 CO 低温氧化催化剂 Au/α-Fe₂O₃, 通过 X 射线衍射、X 射线光电子能谱、N₂ 吸附-脱附、傅里叶变换红外光谱、H₂ 程序升温还原和 CO₂ 程序升温脱附等手段对催化剂进行了表征, 探讨了在室温大气气氛下光线照射以及表面吸附等环境因素所导致的催化剂存贮失活及其作用机理. 结果表明, 经 110 ^oC 干燥的 Au/α-Fe₂O₃催化剂表面同时存在 Au³⁺和 Au^δ+ (0 ≤ δ ≤ 1) 物种, 且前者催化 CO 氧化的活性更高; 在室温大气气氛下, 紫外线照射会引起 Au³⁺的还原和 Au 颗粒的生长, 导致催化剂的不可逆失活. 此外, 空气中的 H₂O 和 CO₂ 可同时吸附在 α-Fe₂O₃的表面, 形成表面碳酸盐物种, 会引起催化剂的可逆失活.     

Solid‐State NMR and DFT Studies on the Formation of Well‐Defined Silica‐Supported Tantallaaziridines: From Synthesis to Catalytic Application

Single‐site, well‐defined, silica‐supported tantallaaziridine intermediates [≡Si‐O‐Ta(η²‐NRCH₂)(NMe₂)₂] [R=Me ( 2 ), Ph ( 3 )] were prepared from silica‐supported tetrakis(dimethylamido)tantalum [≡Si‐O‐Ta(NMe₂)₄] ( 1 ) and fully characterized by FTIR spectroscopy, elemental analysis, and ¹H,¹³C HETCOR and DQ TQ solid‐state (SS) NMR spectroscopy. The formation mechanism, by β‐H abstraction, was investigated by SS NMR spectroscopy and supported by DFT calculations. The C?H activation of the dimethylamide ligand is favored for R=Ph. The results from catalytic testing in the hydroaminoalkylation of alkenes were consistent with the N‐alkyl aryl amine substrates being more efficient than N‐dialkyl amines.     

A protophilic solvent‐assisted solvothermal approach to Cu‐BTC for enhanced CO2 capture

Cu‐BTC–ethylenediamine (EDA)/polyethyleneimine (PEI) adsorbents were synthesized using a protophilic solvent‐assisted solvothermal method. EDA was introduced to enhance the degree of activation due to its lower boiling point allowing it to be removed easily compared with dimethylformamide. A contrast experiment was done by introducing PEI to the solvothermal solution considering its higher boiling point. Powder X‐ray diffraction, scanning electron microscopy and Raman spectroscopic characterizations were performed to investigate the effect of EDA/PEI on crystallinity and morphology of the adsorbents. ¹H NMR characterization and elemental analysis were performed to study the removal rate of organic guest molecules and the degree of activation. Nitrogen physical adsorption and CO₂ adsorption isotherms were used to measure the surface area and CO₂ adsorption capacities. The CO₂ adsorption mechanism of the synthesized adsorbents is mainly dependent on physisorption determined by surface area. Furthermore, open metal sites generated by the enhancement of degree of activation also promote the CO₂ adsorption performance. Therefore, adsorbents synthesized using the protophilic solvent‐assisted solvothermal method exhibit excellent CO₂ adsorption performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Enhanced Formaldehyde‐Vapor Adsorption Capacity of Polymeric Amine‐Incorporated Aminosilicas

Airborne formaldehyde, which is a highly problematic volatile organic compound (VOC) pollutant, is adsorbed by polymeric amine‐incorporated silicas (aminosilicas), and the factors that affect the adsorption performance are systematically investigated. Three different types of polymeric amines 1) poly(ethyleneimine) branched (PEIBR); 2) poly(ethyleneimine) linear (PEILI); and 3) poly(allylamine) (PAA) are impregnated into two types of porous silicas [SBA‐15 and mesocellular foam (MCF) silicas] with systematic changes of the amine loadings. The adsorption results demonstrate that the adsorption capacity increases along with the amine loading until the polymeric amines completely fill the silica pores. This results in the MCF silica, which has a larger pore volume and hence can accommodate more polymeric amine before completely filling the pore, giving materials that adsorb more formaldehyde, with the largest adsorption capacity, q, of up to 5.7 mmol_HCHO g^?1 among the samples studied herein. Of the three different types of polymers, PAA, comprised of 100 % primary amines, showed the highest amine efficiency μ (mmol_HCHO/mmol_N) for capturing formaldehyde. The chemical structures of the adsorbed formaldehyde are analyzed by ¹³C cross‐polarization magic‐angle spinning (CP‐MAS) NMR, and it is demonstrated that the adsorbed formaldehyde is chemically attached to the aminosilica surface, forming hemiaminal and imine species. Because the chemical adsorption of formaldehyde forms covalent bonds, it is not desorbed from the aminosilicas below 130 °C based on temperature‐programed‐desorption (TPD) analysis. The high formaldehyde‐adsorption capacity and stability of the trapped formaldehyde on the amine surface in this study reveal the potential utility of aminosilicas as formaldehyde abatement materials.     

Solution Behaviour and Biomolecular Interactions of Two Cytotoxic trans‐Platinum(II) Complexes Bearing Aliphatic Amine Ligands

A novel trans‐platinum(II) complex bearing one dimethylamine (dma) and one methylamine (ma) ligand, namely trans‐[PtCl₂(dma)(ma)], recently synthesised and characterised in our laboratory, displayed relevant antiproliferative properties in vitro, being more active than the parent complex, trans‐[PtCl₂(dma)(ipa)], which has isopropylamine (ipa) in place of methylamine. We have analysed comparatively the solution behaviour of these two complexes under various experimental conditions, and investigated their reactivity with horse heart cytochrome c by mass spectrometry, inductively coupled plasma–optical emission spectroscopy (ICP‐OES), 2D [¹H,¹⁵N],[¹H,¹³C] HSQC and [¹H,¹H] NOESY NMR. Some important changes that occurred in the [¹H,¹³C] HSQC NMR spectrum of cytochrome c treated with trans‐[PtCl₂(dma)(ma)] in water, after two days’ incubation, most probably arose from direct platinum coordination to the protein side chain; this was proved conclusively by [¹H,¹H] NOESY NMR and [¹H,¹⁵N] HSQC NMR measurements. Met65 was identified as the primary Pt binding site on cytochrome c. Electrospray mass spectrometry (ESIMS) results provided evidence for extensive platinum–protein adduct formation. A fragment of the [Pt(amine)(amine′)] type was established to be primarily responsible for protein metalation. ICP‐OES analysis revealed that these trans‐platinum(II) complexes bind preferentially to the serum proteins albumin and transferrin rather than to calf thymus DNA. Pt binding to DNA was found to be far lower than in the case of cisplatin. The implications of the results for the mechanism of action of novel cytotoxic trans‐platinum complexes are discussed.     

Synthesis,Characterization, and Properties of a Carbonate‐Bridged Dinuclear Rhodium(III) Complex via Fixation of Atmospheric CO2

A carbonate‐bridged rhodium(III) dimeric complex of formula μ‐CO₃‐[(ppy)₂Rh]₂, (ppy = 2‐phenylpyridine) was synthesized and characterized by IR and ¹H NMR spectroscopy as well as X‐ray diffraction. The bridging carbonate ion presumably originates from the capture of CO₂ in air deduced on a series of control experiments, which may have valuable implications for the study of fixation of CO₂. The luminescent and thermal properties of this complex were also investigated.     

超声波技术制备功能化二氧化硅在苯酚和碳酸二甲酯甲基化反应中的应用

Porous silica modified with -（CH2）3NH2 （primary amine）, -（CH2）3NHCH2CH2NH2 （secondary/primary amine） and -（CH2）3N-cycl-（CH2）4 （tertiary amine） were synthesized by ultrasonic technique under mild conditions. The samples were characterized by BET, elemental analysis and TG, showing that the organosilane moieties were grafted onto the surface of porous silica by covalent bond. The structure of the organosilane moieties and ultrasonic treatment time were all significant for the quantities of grafted amino groups. The samples exhibited promising catalytic properties towards the methylation reaction of phenol with dimethyl carbonate （DMC）. The methylation reaction with the modified samples featured high selectivity at high conversion. The samples were subjected to utilization for a few recycles without obvious loss of activity to indicate that ultrasonic technique was effective for the preparation of organically modified porous silica catalysts.     

Self‐Assembly of 3,6‐Bis(4‐triazolyl)pyridazine Ligands with Copper(I) and Silver(I) Ions: Time‐Dependant 2D‐NOESY and Ultracentrifuge Measurements

Two 3,6‐bis(R‐1H‐1,2,3‐triazol‐4‐yl)pyridazines (R=mesityl, monodisperse (CH₂ CH₂O)₁₂CH₃) were synthesized by the copper(I)‐catalyzed azide–alkyne cycloaddition and self‐assembled with tetrakis(acetonitrile)copper(I) hexafluorophosphate and silver(I) hexafluoroantimonate in dichloromethane. The obtained copper(I) complexes were characterized in detail by time‐dependent 1D [¹H, ¹³C] and 2D [¹H‐NOESY] NMR spectroscopy, elemental analysis, high‐resolution ESI‐TOF mass spectrometry, and analytical ultracentrifugation. The latter characterization methods, as well as the comparison to analog 3,6‐di(2‐pyridyl)pyridazine (dppn) systems and their corresponding copper(I) and silver(I) complexes indicated that the herein described 3,6‐bis(1H‐1,2,3‐triazol‐4‐yl)pyridazine ligands form [2×2] supramolecular grids. However, in the case of the 3,6‐bis(1‐mesityl‐1H‐1,2,3‐triazol‐4‐yl)pyridazine ligand, the resultant red‐colored copper(I) complex turned out to be metastable in an acetone solution. This behavior in solution was studied by NMR spectroscopy, and it led to the conclusion that the copper(I) complex transforms irreversibly into at least one different metal complex species.