Adsorbed CO Molecules Research Articles

“Partition Method”-Inspired Fabrication of Hierarchically Porous Polyetherimide via Supercritical CO2 Foaming: Achieving Efficient Adsorption of Carbon Dioxide

Although supercritical carbon dioxide foaming technology has achieved significant advances in the fabrication of porous polymers, the slow adsorption of carbon dioxide and the high melt strength of engineering plastics make it difficult to foam. Herein, the “partition method” is used to divide block polyetherimide (PEI) into many tiny parts through the interconnected pores to realize the rapid adsorption of CO2 molecules. Specifically, an adsorption capacity of 9.18 wt % for porous PEI was obtained at 35 °C for just 1 h which was considerably higher than that of 4.36 wt % for non-porous PEI. Then, PEI with a uniform and ordered hierarchically porous structure (micro- and nanoscale) was successfully prepared by external force-induced cell nucleation growth. Meanwhile, this treatment has little effect on the thermal properties of the polymer. This green strategy applies to other general plastics, for example, polystyrene, and paves the way for designing large-scale hierarchically porous components such as porous bearing cages, tissue engineering scaffolds, and thermal insulation foam.

A mesh cladding-structured Sr-doped LaFeO3/Bi4O5Br2 photocatalyst: Integration of oxygen vacancies and Z-scheme heterojunction toward enhanced CO2 photoreduction

Solar-driven conversion of CO2 into beneficial chemical fuels using photocatalysts is a sustainable approach for obtaining renewable energy. However, the poor photoabsorption, low charge separation efficiency, and sluggish interfacial reaction due to a paucity of active sites limit the photocatalytic activity. Herein, a mesh cladding structure of Sr-doped LaFeO3/Bi4O5Br2 (Sr-LFO/BOB) Z-scheme heterojunction with abundant surface oxygen vacancies (OVs) is developed to improve the CO2 photoreduction. Sr doping in LFO introduce OVs, which captures more photoinduced electrons contributing to the surface adsorption of CO2 molecules and narrows the LFO band gap extending the light absorption range to the whole visible spectrum. Particularly, the unique mesh cladding heterostructure composed of Sr-LFO particles wrapped with BOB nanowires provides ample Z-scheme charge-transfer pathways at the Sr-LFO/BOB and sufficiently exposes Sr-LFO surface for CO2 adsorption. Benefiting from the OVs and design of Z-scheme, the optimized photocatalyst (0.05Sr-LFO/BOB(2)) with appropriate Sr doping (5%) and BOB content demonstrates a considerable CH4 generation of 10.14 μmol g−1, which is approximately 48.3-fold higher than that of the pristine LFO. This study provides an insight into the design and fabrication of high-performance perovskite oxide-based photocatalysts by constructing a Z-scheme heterojunction with abundant active sites for CO2 photoreduction.

Gas sensing potential of monolayer MoB: A first principles study

Monolayer MoB is one of MBenes with a structure similar to graphene. Through first-principles calculations, we have investigated the adsorption characteristics of monolayer MoB for CO, NO, SO, SO2 gases. The results show that CO and NO tend to adsorb at the top of Mo, and SO and SO2 tend to adsorb at the top of B. The adsorption energies of all gas molecules are negative, with the smallest adsorption energy for SO. All gas molecules are charge acceptors, with SO2/MoB having the largest charge transfer value of 0.977 eV. According to the transition state theory, the shortest recovery time for monolayer MoB adsorbed CO molecule. This means that the process of CO adsorption by monolayer MoB is reversible and monolayer MoB has the potential to be used as a CO gas detection sensor. At room temperature, it is almost impossible for monolayer MoB to recover its initial state after adsorption of NO, SO and SO2. In addition, MoB has high sensitivity in detecting NO, SO and SO2 due to its low adsorption energy for NO, SO and SO2, and has the potential to be a sensitive irreversible detection sensor for detecting NO, SO and SO2.

CO oxidation over CuOx/TiO2 catalyst: The importance of oxygen vacancies and Cu+ species

It is well documented that the existence of oxygen vacancies and active Cu species can improve CO oxidation activity over TiO2 substrate. Herein, TiO2-supported copper catalysts (CuOx/TiO2) with different ratio of oxygen vacancies (Ov) and Cu+ has been synthesized. The existence and amount of Ov and Cu+ species were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectrum (EPR). The synergetic effect between Cu+ and oxygen vacancies was investigated in terms of O2 temperature-programmed desorption (O2–TPD), H2 temperature-programmed reduction (H2–TPR) and in situ DRIFTS spectra. Cu+ is the adsorption site for CO molecules, the abundant Ov can significantly activate molecular oxygen, which effectively oxidize the adsorbed CO molecules. The most suitable ratio between Cu+ and Ov has been confirmed. The CuOx/TiO2(Cu+ rich) catalyst (51% Cu+, 26.3% Ov) shows superior CO oxidation activity (T90 = 136 °C) compared to CuOx/TiO2(Ov rich) catalyst (39% Cu+, 28.5% Ov, T90 > 350 °C). This work provides comprehensive investigation of the role for abundant oxygen vacancies and Cu+ in CO oxidation reactions.

Ab Initio Investigation of the Adsorption of CO2 Molecules on Defect Sites of Graphene Surfaces: Role of Local Vacancy Structures.

An in-depth investigation into the adsorption of CO2 on graphene vacancies is essential for the understanding of their applications in various industries. Herein, we report an investigation of the effects of vacancy defects on CO2 gas adsorption behavior on graphene surfaces using the density functional theory. The results show that the formation of vacancies leads to various deformations of local carbon structures, resulting in different adsorption capabilities. Even though most carbon atoms studied can only trigger physisorption, there are also carbon sites that are energetically favored for chemisorption. The general order of the adsorption capabilities of the local carbon atoms is as follows: carbon atoms with dangling bonds > carbon atoms shared by five- and six-membered rings and a vacancy > carbon atoms shared by two six-membered rings and a vacancy. A stronger interaction in the adsorption process generally corresponds to more obvious changes in the partial density of states and a larger amount of transferred charge.

Preferred surface orientation for CO oxidation on SnO2 surfaces.

In the present study, we perform a comparative study on the oxidation mechanism of CO gas molecules on SnO2 (110), (101), and (100) surfaces. The optimized adsorption configurations show that the adsorption of CO molecules could occur similarly on the three SnO2 surfaces via two adsorption modes, physisorption of CO on the Sn5c site that is considered as the first step for CO oxidation, followed by CO chemisorption on the O2c site resulting in the formation of CO2 species. Based on the calculated adsorption energies and CO molecule diffusion on SnO2 surfaces, CO molecule adsorption on the (101) surface exhibits the highest adsorption energy and the lowest reaction barrier for CO oxidation compared to the widely considered (110) surface or the (100) surface. These findings are expected to have a major impact on improving sensing properties toward toxic gas by means of surface-orientation engineering.

Approaches to the design of efficient and stable catalysts for biofuel reforming into syngas: doping the mesoporous MgAl2O4 support with transition metal cations.

The mesoporous MgAl2O4 support is promising for the design of efficient and stable to coking catalysts for natural gas and biofuel reforming into syngas. This work aims at doping this support with transition metal cations (Fe, Cr, Ti) to prevent the incorporation of Ni and rare-earth cations (Pr, Ce, Zr), loaded by impregnation, into its lattice along with providing additional sites for CO2 activation required to prevent coking. Doped MgAl1.9Me0.1O4 (Me = Fe, Ti, Cr) mesoporous supports prepared by the one-pot evaporation-induced self-assembly method with Pluronic P123 triblock copolymers were single-phase spinels. Their specific surface area varies in the range of 115-200 m2 g-1, decreasing to 90-110 m2 g-1 after successive addition of the supporting nanocomposite active component 10 wt% Pr0.3Ce0.35Zr0.35O2 + (5 wt% Ni + 1% Ru) by impregnation. Mössbauer spectroscopy for iron-doped spinels confirmed the spatially uniform distribution of Fe3+ cations in the lattice without clustering being mainly located at the octahedral positions. Fourier-transform infrared spectroscopy of the adsorbed CO molecules was performed to estimate the surface density of metal sites. In methane dry reforming, the positive effect of MgAl2O4 support doping was observed from both a higher turn-over frequency as compared with the catalyst on the undoped support as well as the highest efficient first-order rate constant for the Cr-doped catalyst as compared with published data for a variety of Ni-containing catalysts based on the alumina support. In the reaction of ethanol steam reforming, the efficiency of catalysts on the doped supports is comparable, while exceeding that of Ni-containing supported catalysts reported in the literature. Coking stability was provided by a high oxygen mobility in the surface layers estimated by the oxygen isotope heteroexchange with C18O2. A high efficiency and coking stability were demonstrated in the reactions of methane dry reforming and ethanol dry and steam reforming in concentrated feeds for the honeycomb catalyst with a nanocomposite active component on the Fe-doped MgAl2O4 support loaded on the FeCrAl-alloy foil substrate.

Guest-induced pore breathing controls the spin state in a cyanido-bridged framework.

Iron(ii) spin cross-over (SCO) compounds combine a thermally driven transition from the diamagnetic low-spin (LS) state to the paramagnetic high-spin (HS) state with a distinct change in the crystal lattice volume. Inversely, if the crystal lattice volume was modulated post-synthetically, the spin state of the compound could be tunable, resulting in the inverse effect for SCO. Herein, we demonstrate such a spin-state tuning in a breathing cyanido-bridged porous coordination polymer (PCP), where the volume change resulting from guest-induced gate-opening and -closing directly affects its spin state. We report the synthesis of a three-dimensional coordination framework {[FeII(4-CNpy)4]2[WIV(CN)8]·4H2O}n (1·4H2O; 4-CNpy = 4-cyanopyridine), which demonstrates a SCO phenomenon characterized by strong elastic frustration. This leads to a 48 K wide hysteresis loop above 140 K, but below this temperature results in a very gradual and incomplete SCO transition. 1·4H2O was activated under mild conditions, producing the nonporous {[FeII(4-CNpy)4]2[WIV(CN)8]}n (1) via a single-crystal-to-single-crystal process involving a 7.3% volume decrease, which shows complete and nonhysteretic SCO at T1/2 = 93 K. The low-temperature photoswitching behavior in 1 and 1·4H2O manifested the characteristic elasticity of the frameworks; 1 can be quantitatively converted into a metastable HS state after 638 nm light irradiation, while the photoactivation of 1·4H2O is only partial. Furthermore, nonporous 1 adsorbed CO2 molecules in a gated process, leading to {[FeII(4-CNpy)4]2[WIV(CN)8]·4CO2}n (1·4CO2), which resulted in a 15% volume increase and stabilization of the HS state in the whole temperature range down to 2 K. The demonstrated post-synthetic guest-exchange employing common gases is an efficient approach for tuning the spin state in breathing SCO-PCPs.

Carbon dioxide adsorption to UiO-66: theoretical analysis of binding energy and NMR properties.

UiO-66 is one of the most valuable metal-organic frameworks because of its excellent adsorption capability for gas molecules and its high stability towards water. Herein we investigated adsorption of carbon dioxide (CO2), acetone, and methanol to infinite UiO-66 using DFT calculations on an infinite system under periodic-boundary conditions and post-Hartree-Fock (SCS-MP2 and MP2.5) calculations on cluster models. Three to four molecules are adsorbed at each of four μ-OH groups bridging three Zr atoms in one unit cell (named Site I). Six molecules are adsorbed around three pillar ligands, where the molecule is loosely surrounded by three terephthalate ligands (named Site II). Also, six molecules are adsorbed around the pillar ligand in a different manner from that at Site II, where the molecule is surrounded by three terephthalate ligands (named Site III). Totally fifteen to sixteen CO2 molecules are adsorbed into one unit cell of UiO-66. The binding energy (BE) decreases in the order Site I > Site III > Site II for all three molecules studied here and in the order acetone > methanol ≫ CO2 in the three adsorption sites. At the site I, the protonic H atom of the μ-OH group interacts strongly with the negatively charged O atom of CO2, acetone and methanol, which is the origin of the largest BE value at this site. Although the DFT calculations present these decreasing orders of BE values correctly, the correction by post-Hartree-Fock calculations is not negligibly small and must be added for obtaining better BE values. We explored NMR spectra of UiO-66 with adsorbed CO2 molecules and found that the isotropic shielding constants of the 1H atom significantly differ among no CO2, one CO2 (at Sites I, II, or III), and fifteen CO2 adsorption cases (Sites I to III) but the isotropic 17O and 13C shielding constants change moderately by adsorption of fifteen CO2 molecules. Thus, 1H NMR measurement is a useful experiment for investigating CO2 adsorption.

An in silico study of the selective adsorption and separation of CO2 from a flue gas mixture (CH4, CO2, N2) by ZnLi5+ clusters.

Due to the increasing concentration of CO2 in the atmosphere and its negative effect on the environment, selective adsorption of CO2 from flue gas has become significantly important. In this study, we have considered a Zn-doped lithium cluster, ZnLi5+ cluster, featuring a planar pentacoordinate Zn centre, as a potential candidate for selective CO2 capture and separation from a flue gas mixture (CH4, CO2, N2). The binding energy calculation and non-covalent interaction study showed that CO2 molecules bind relatively strongly as compared to N2 and CH4 molecules. The metal cluster can bind five CO2, five CH4, and four N2 molecules with average binding energies of -9.2, -4.4, and -6.1 kcal mol-1, respectively. Decomposition of the binding energy through symmetry-adapted perturbation theory analysis reveals that the electrostatic component plays a major role. The cationic cluster may be a promising candidate for selective CO2 capture and can be used as a pollution-controlling agent. The calculated adsorption energy of H2S is quite closer to that of CO2, suggesting competitive adsorption between CO2 and H2S. The adsorption energies of H2O and NH3 are higher compared to CO2, indicating that these gases may be a potential threat to CO2 capture.

Theoretical understanding of the effect of specifically adsorbed halide anions on Cu-catalyzed CO2 electroreduction activity and product selectivity.

Initial CO2 electroreduction into CO and its subsequent electroreduction pathways were selected to study the effect of specifically adsorbed halide anions X- (X = F, Cl, Br, I) on CO2 electroreduction activity and product selectivity at Cu(111)/H2O interfaces via DFT calculations. The calculated results show that the presence of halide anions can exert a notable effect on the CO2 adsorption characteristics and that chemically adsorbed CO2 molecules can be formed. Furthermore, the halide-anion-modified Cu(111)/H2O interfaces could significantly enhance the initial CO2 electroreduction into CO activity, which is regarded as the rate-determining step during CO2 electroreduction at clean Cu(111)/H2O interfaces. Analysis of the initial CO2 electroreduction and Volmer reaction pathways showed that the halide-anion-modified Cu(111)/H2O interfaces could suppress the HER and thus improve the CO2 electroreduction activity and product selectivity. It is speculated that the enhanced initial CO2 electroreduction activity at the F--, Cl--, Br--, and I--modified Cu(111)/H2O interfaces may originate from the decreased work functions and anion radical ·CO2- formations. Simultaneously, we concluded that dimer OCCO formations in the presence of halide anions were more favorable than CHO during CO electroreduction according to the order of I- > Br- > Cl- > F- and could result in the production of C2 product, suggesting an improved CO2 electroreduction product selectivity. The present analyses of electronic structure may explain the more favorable OCCO formations in the order of I- > Br- > Cl- > F-. The present understanding of this effect will provide an improved scientific guideline for the control of CO2 electroreduction pathways and design of more efficient electrocatalysts.

Evolution of surface and bulk structure of supported palladium nanoparticles by in situ X-ray absorption and infrared spectroscopies: Effect of temperature, CO and CH4 gas

Interaction of CO and CH4 with palladium is a relevant process in numerous catalytic reactions, which may induce structural changes in the metal affecting its catalytic properties This work establishes a systematic study of the evolution of the atomic and electronic structure in alumina- and carbon-supported palladium nanoparticles in presence of CO and CH4 gases at temperatures from 50 to 350 °C by a combination of in situ X-ray absorption and infrared spectroscopies. Immediate adsorption of CO molecules with formation of surface carbon deposits due to the disproportionation reaction occurs at low temperatures, while above 250 °C, active formation of bulk palladium carbide is observed. In CH4 the later process starts only at ca. 350 °C. Reduction of palladium and contraction of the Pd-Pd interatomic distances were observed with increasing temperature irrespective of the gas atmosphere, including the inert one, particle size and the type of support. For carbon supported samples formation of palladium carbide occurred above 200 °C due to the decomposition of the support.

Polyethyleneimine-Starch Functionalization of Single-Walled Carbon Nanotubes for Carbon Dioxide Sensing at Room Temperature.

There is an ever-growing interest in the detection of carbon dioxide (CO2) due to health risks associated with CO2 emissions. Hence, there is a need for low-power and low-cost CO2 sensors for efficient monitoring and sensing of CO2 analyte molecules in the environment. This study reports on the synthesis of single-walled carbon nanotubes (SWCNTs) that are functionalized using polyethyleneimine and starch (PEI-starch) in order to fabricate a PEI-starch functionalized SWCNT sensor for reversible CO2 detection under ambient room conditions (T = 25 °C; RH = 53%). Field-emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy are used to analyze the physiochemical properties of the as-synthesized gas sensor. Due to the large specific surface area of SWCNTs and the efficient CO2 capturing capabilities of the amine-rich PEI layer, the sensor possesses a high CO2 adsorption capacity. When exposed to varying CO2 concentrations between 50 and 500 ppm, the sensor response exhibits a linear relationship with an increase in analyte concentration, allowing it to operate reliably throughout a broad range of CO2 concentrations. The sensing mechanism of the PEI-starch-functionalized SWCNT sensor is based on the reversible acid-base equilibrium chemical reactions between amino groups of PEI and adsorbed CO2 molecules, which produce carbamates and bicarbonates. Due to the presence of hygroscopic starch that attracts more water molecules to the surface of SWCNTs, the adsorption capacity of CO2 gas molecules is enhanced. After multiple cycles of analyte exposure, the sensor recovers to its initial resistance level via a UV-assisted recovery approach. In addition, the sensor exhibits great stability and reliability in multiple analyte gas exposures as well as excellent selectivity to carbon dioxide over other interfering gases such as carbon monoxide, oxygen, and ammonia, thereby showing the potential to monitor CO2 levels in various infrastructure.

Understanding the effects of cluster restructuring on water gas shift reaction over Cu/TM (TM = Cu, Ni and Pt) under high concentration of CO

Ambient pressure and resulting cluster restructuring have been proved to influence water gas shift reaction (WGSR), but the intrinsic role that high concentration of CO and cluster surface play during WGSR is still elusive. In this work, the rationale behind the dual effects of CO concentration and cluster condensation on WGSR over Cu-based bimetallic alloys is theoretically revealed using density functional theory (DFT) approach. The results demonstrate that the additional adsorption of CO molecules inhibits WGSR thermodynamically and kinetically. Specifically, the increase of concentration weakens the molecule adsorption (CO and water-related molecules) and hinders the development of intermediate evolutions in WGSR, while the cluster restructuring simultaneously raises the activation energy of water dissociation. The charge density difference and Bader distribution provide electronic support for the above conclusions. Furthermore, Cu/Ni is considered as the preferential catalyst under high concentration of CO, not only because of the remarkable adsorption capacity, but also the fine structure-catalytic stability. The selection of cluster shape and energy-temperature characteristics of intermediates are also introduced, enriching the understanding of group reactivity on copper based catalysts.

Carbon sequestration in graphene oxide modified cementitious system

Graphene oxide is emerging as a promising nanomaterial owing to its unique property of being a strong and flexible material. This work examines the potential use of graphene oxide (GO) for CO2 sequestration in cementitious-based materials in addition to mechanical properties. The effect of oxidized graphene surface on the hydration mechanism of cement paste and carbonate mineralization was investigated. Experimental results show that the application of GO at optimum amount offers 40% improvement in compressive strength at an early age. Accelerated carbon curing of GO-cement matrix was performed to evaluate CO2 sequestration through thermogravimetric analysis and results revealed that adding a low concentration of GO (i.e. 0.05%) improved CO2 uptake by 30% in the cementitious system. Further, physical adsorption of CO2 molecules and alteration in C–S–H was confirmed by the FTIR study. This finding suggests that the application of GO, not only improved the mechanical properties but it significantly enhanced the CO2 sequestration in cementitious systems.

High pressure CO2 adsorption onto Malaysian Mukah-Balingian coals: Adsorption isotherms, thermodynamic and kinetic investigations

CO2 sequestration into coalbed seams is one of the practical routes for mitigating CO2 emissions. The adsorption mechanisms of CO2 onto Malaysian coals, however, are not yet investigated. In this research CO2 adsorption isotherms were first performed on dry and wet Mukah-Balingian coal samples at temperatures ranging from 300 to 348 K and pressures up to 6 MPa using volumetric technique. The dry S1 coal showed the highest CO2 adsorption capacity of 1.3 mmol g−1, at 300 K and 6 MPa among the other coal samples. The experimental results of CO2 adsorption were investigated using adsorption isotherms, thermodynamics, and kinetic models. Nonlinear analysis has been employed to investigate the data of CO2 adsorption onto coal samples via three parameter isotherm equilibrium models, namely Redlich Peterson, Koble Corrigan, Toth, Sips, and Hill, and four parameter equilibrium model, namely Jensen Seaton. The results of adsorption isotherm suggested that the Jensen Seaton model described the experimental data well. Gibb's free energy change values are negative, suggesting that CO2 adsorption onto the coal occurred randomly. Enthalpy change values in the negative range established that CO2 adsorption onto coal is an exothermic mechanism. Webber's pore-diffusion model, in particular, demonstrated that pore-diffusion was the main controlling stage in CO2 adsorption onto coal matrix. The activation energy of the coals was calculated to be below −13 kJ mol−1, indicating that adsorption of CO2 onto coals occurred through physisorption. The results demonstrate that CO2 adsorption onto coal matrix is favorable, spontaneous, and the adsorbed CO2 molecules accumulate more onto coal matrix. The observations of this investigation have significant implications for a more accurate measurement of CO2 injection into Malaysian coalbed seams.

Ultrathin ZnIn2S4 nanosheet arrays activated by nitrogen-doped carbon for electrocatalytic CO2 reduction reaction toward ethanol

Ternary ZnIn2S4 (ZIS) is a kind of potential electrocatalyst for CO2 reduction reaction (CO2RR). However, the reported reduction products are usual C1 species. Considering that N doped carbon can increase adsorption of CO2 molecules, facilitate electron transfer, and activate active sites, here ultrathin ZIS nanosheet arrays (ZIS NSAs) grown on N doped carbon cloth (NDCC) were synthesized through a facile hydrothermal route. The as-synthesized ZIS NSAs/NDCC enabled electrocatalytic CO2RR toward ethanol with the highest 42 % faradaic efficiency (FE) at an applied potential of − 0.7 V versus the reversible hydrogen electrode (RHE) in CO2-saturated 0.5 M KHCO3 aqueous solution. This is first report on ZIS-based electrocatalyst for electrocatalytic CO2RR toward ethanol production. The experimental results and density functional theory (DFT) calculations showed that NDCC could enhance the CO2RR activity and promote CO-CO coupling process. Our work not only provides a new electrocatalyst for CO2RR to ethanol but also stresses the influence of N doped carbon substrate and bimetallic effect on electrocatalytic CO2RR.

Hydroxy-Rich Pillar[5]arene-Based Nanoporous Aromatic Frameworks (PAFs) for Efficient CO2 Uptake under Ambient Conditions

In this letter, we report our fabrication of a three-dimensional hydroxy-rich pillar[5]arene-extended nanoporous aromatic framework PAF-P5-OH for CO2 uptake. CO2 adsorption study demonstrated that PAF-P5-OH exhibited excellent CO2 uptake capacity (88 cm3 g–1 at 273 K and 76 cm3 g–1 at 298 K) under atmospheric pressure, which could be attributed to the favored dipole interactions between the adsorbed CO2 molecules and the hydroxy groups in PAF-P5-OH.

Adsorption application of tetraethylenepentamine (TEPA) modified SBA-15@MIL-101(Cr) in carbon capture and storage (CCS)

To design a better carbon capture material, a SBA-15@MIL-101(Cr) composite is prepared by an in situ synthesis method, and its adsorption performance is enhanced by TEPA modification. The SBA-15 with well-ordered mesopores acted as a carrier, which regulated the growth of MIL-101(Cr) crystals. The silicon hydroxyl group in SBA-15 stably binds to TEPA in the form of hydrogen bond, and the Lewis acid site (CUS) in MIL-101(Cr) makes it bind to TEPA in coordination bond. The unique pore cage structure of MIL-101(Cr) and the basic site provided by TEPA make the material contain both physical and chemical adsorption forces in the process of adsorption of CO2 molecules. The good thermal stability of SBA-15 improves the thermal stability of MIL-101(Cr) and TEPA in the SBA-15 channel. Compared with the original MIL-101(Cr), the composite and modified materials showed higher CO2 absorption capacity at 298K and 100 kPa. By fitting the Langmuir equation and Freundlich equation, it can be found that the adsorption behavior of the materials after TEPA loading has the non-uniformity of surface binding. The adsorption behavior is a typical exothermic process, so the adsorption capacity of the material is inversely proportional to the temperature. Compared with other similar materials, the materials designed in this work have good CO2 adsorption energy per unit area, and also have good reusability. Therefore, this study opens a new way for the design of graded porous amine-modified MOF-based materials with advanced gas adsorption properties.

NaCl-Templated Ultrathin 2D-Yttria Nanosheets Supported Pt Nanoparticles for Enhancing CO Oxidation Reaction.

Morphology of support is of fundamental significance to the fabrication of highly efficient catalysts for CO oxidation reaction. Many methods for the construction of supports with specific morphology and structures greatly rely on controlling general physical and chemical synthesis conditions such as temperature or pH. In this paper, we report a facile route to prepare yttria nanosheet using NaCl as template to support platinum nanoparticles exhibiting higher CO oxidation activity than that of the normally prepared Pt/Y2O3. With the help of TEM and SEM, we found that Pt NPs evenly distributed on the surface of NaCl modified 2D-nanosheets with smaller size. The combination of XAFS and TEM characterizations demonstrated that the nano-size Pt species with PtxOy structure played an essential role in the conversion of CO and kept steady during the CO oxidation process. Moreover, the Pt nanoparticles supported on the NaCl templated Y2O3 nanosheets could be more easily reduced and thus exposed more Pt sites to adsorb CO molecules for CO oxidation according to XPS and DRIFTS results. This work offers a unique and general method for the preparation of potential non-cerium oxide rare earth element oxide supported nanocatalysts.