Diffuse Reflectance Infrared Fourier Transform Research Articles

Furfural adsorption on V2O5 surface: A combined experimental-theoretical study

The adsorption of furfural on the V2O5 surface was investigated using experimental and theoretical methods. In situ Diffuse Reflectance Infrared Fourier-Transform Spectroscopy results show the presence of physi- and chemi-sorption phenomena, where trans-furfural is mostly chemisorbed at the beginning of the adsorption process. These results are in agreement with theoretical DFT results, as the most thermodynamically favored configurations corresponds to the chemisorbed trans-furfural (T1) and cis-furfural (C1) with binding energies of −1.83 and −2.05 eV.

Ce-based three-dimensional mesoporous microspheres with Mn homogeneous incorporation for toluene oxidation

Ce-based three-dimensional (3D) mesoporous microspheres with Mn homogeneous incorporation were synthesized. The CeMn-0.4, characterized by a Ce/Mn molar ratio of 6:4, demonstrated exceptional catalytic activity and stability. The formation of CeMn solid solution strengthened the Ce-Mn interaction, yielding higher concentrations of Ce3+ and Mn4+. Mn4+ initiated toluene preliminary activation owing to its robust oxidative properties, while Ce3+ contributed to oxygen vacancy generation, enhancing the activation of gaseous oxygen and lattice oxygen mobility. Integrating experiments and Density Functional Theory (DFT) calculations elucidated the oxygen reaction mechanisms. A portion of oxygen was converted into surface reactive oxygen species (Oads) that directly oxidized toluene. Additionally, the presence of oxygen vacancies promoted the participation of oxygen in toluene oxidation by converting it into lattice oxygen, which was crucial for the deep oxidation of toluene. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) indicated the accumulation of benzene-ring intermediates on the catalyst surface hindered continuous toluene oxidation. Thus, the abundant oxygen vacancies in CeMn-0.4 played a pivotal role in sustaining the oxidation process by bolstering the activation of gaseous oxygen and the mobility of lattice oxygen.

Construction of an Electron Capture and Transfer Center for Highly Efficient and Selective Solar-Light-Driven CO2 Conversion.

Exploring high-efficiency photocatalysts for selective CO2 reduction is still challenging because of the limited charge separation and surface reactions. In this study, a noble-metal-free metallic VSe2 nanosheet was incorporated on g-C3N4 to serve as an electron capture and transfer center, activating surface active sites for highly efficient and selective CO2 photoreduction. Quasi in situ X-ray photoelectron spectroscopy (XPS), soft X-ray absorption spectroscopy (sXAS), and femtosecond transient absorption spectroscopy (fs-TAS) unveiled that VSe2 could capture electrons, which are further transferred to the surface for activating active sites. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations revealed a kinetically feasible process for the formation of a key intermediate and confirmed the favorable production of CO on the VSe2/PCN (protonated C3N4) photocatalyst. As an outcome, the optimized VSe2/PCN composite achieved 97% selectivity for solar-light-driven CO2 conversion to CO with a high rate of 16.3 μmol·g-1·h-1, without any sacrificial reagent or photosensitizer. This work offers new insights into the photocatalyst design toward highly efficient and selective CO2 conversion.

SO2- and H2O-tolerant catalytic reduction of NOx at low temperatures through shielding ceria-based catalyst from poisoning: An efficient protection mechanism

Improving SO2/H2O resistance at low temperatures is a key challenge for industrial applications of NH3-SCR catalysts. Herein, a novel catalyst with remarkable low-temperature NH3-SCR activity and strong SO2/H2O resistance was designed by loading MoOx protective layer over porous kit-CeO2. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) coupled with basic characterization techniques were utilized to further elucidate the underlying mechanisms, and a dynamic balance between the deposition and decomposition of ammonia bisulfate was captured over porous kit-CeO2. Highly dispersed MoOx species pre-adsorbed with NH3 significantly curtailed the adsorption of NOx molecules, and the catalytic reaction over MoOx/kit-CeO2 primarily followed by the Eley-Rideal mechanism. At 250 °C, in the presence of SO2 and H2O, the Ce-O-Mo pairing site was almost unaffected and the super SO2- and H2O-tolerant property originated from the facilitated decomposition of ammonium bisulfate (ABS) and the shielding effect of Mo protective layer on SO2/H2O. This study provided an important guidance to the application of ceria-based catalysts for environmental control within low-temperature operations in non-power industries such as glass, steel, cement manufacturing, etc.

Enhanced performance of attapulgite-supported g-C3N4 for photocatalytic CO2 reduction

As a new type of non-metallic semiconductor photocatalyst, g-C3N4 has great potential in photocatalytic CO2 reduction. However, due to the low catalytic activity, it is still far from industrial reality for such applications. Herein, this work introduces attapulgite (ATP) into the photocatalyst system of g-C3N4. Additionally, ATP/Au-CN was obtained through the photodeposition method. The photocatalytic reduction ability of the photocatalyst for CO2 is enhanced. The photoelectric tests show that loading of ATP can promote the separation and migration of photocarriers. Through BET testing, it was found that the alkaline pore structure on the surface of ATP not only captures CO2, but also increases the specific surface area of the composite. According to the experimental results, the possible photocatalytic mechanism was verified by in-situ diffuse reflection infrared Fourier transform (DRIFT) spectral analysis and DFT calculation. This work provides new guidance for the construction of high efficient photocatalyst systems using abundant ATP as a support.

Efficient Lead Removal by Assembly of Bio-Derived Ellagate Framework, Which Enables Electrocatalytic Reduction of CO2 to Formate.

Lead (Pb) poisoning and CO2-induced global warming represent two exemplary environmental and energy issues threatening humanity. Various biomass-derived materials are reported to take up Pb and convert CO2 electrochemically into low-valent carbon species, but these works address the problems separately rather than settle the issues simultaneously. In this work, cheap, natural ellagic acid (EA) extracted from common plants is adopted to assemble a stable metal-organic framework (MOF), EA-Pb, by effective capture of Pb2+ ions in an aqueous medium (removal rate close to 99%). EA-Pb represents the first structurally well-defined Pb-based MOF showing selective electrocatalytic CO2-to-HCOO- conversion with Faradaic efficiency (FE) of 95.37% at -1.08V versus RHE. The catalytic mechanism is studied by 13CO2 labeling, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and theoretical calculation. The use of EA-Pb as an electrocatalyst for CO2 reduction represents a 2-in-1 solution of converting detrimental wastes (Pb2+) as well as natural resources (EA) into wealth (electrocatalytic EA-Pb) for addressing the global warming issue.

Enhanced mineralization capacity for photocatalytic toluene degradation over Ag3PO4/TiO2: the critical role of oxygen vacancy

Mesoporous disk-like Ag3PO4/TiO2 heterojunctions with rich oxygen vacancies using MIL-125(Ti)-derived TiO2 as support were prepared for photocatalytic degradation toward toluene. The low amount of Ag3PO4 into Ag3PO4/TiO2-10 (1.7 wt% Ag3PO4) greatly improved the toluene mineralization capacity up to 95 %, which was much higher than that of the TiO2 alone (41.3 %). In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) directly verified that the benzene ring was opened rapidly by the Ag3PO4/TiO2-10, while intermediate (like benzaldehyde and benzoic acid) accumulation occurred using pristine TiO2 as photocatalyst. It was demonstrated that Z-scheme heterojunction was formed between Ag3PO4 and TiO2, in which the photo-induced electrons were transferred from conduction band (CB) of the Ag3PO4 to valence band (VB) of the TiO2 under photoexcitation, boosting the generation of reactive oxygen species and inhibiting the photocorrosion of Ag3PO4. Interestingly, quantitative structure-activity relationship suggested that oxygen vacancies as crucial active sites both activated molecular oxygen and captured the photo-induced electrons to form •O2− that dominated in toluene mineralization. This work proved that the construction of Z-scheme heterojunction between MIL-125(Ti)-derived TiO2 and Ag3PO4 solved the inactivation of TiO2 and photocorrosion of Ag3PO4 in photocatalysis, highlighting the role of oxygen vacancy in determining the active species and mineralization degree for photocatalytic toluene elimination.

The impact of indium and manganese modifiers on the catalytic properties of zinc-alumina propane dehydrogenation catalysts

Supported zinc-containing catalysts are considered as a viable alternative to the currently-deployed Cr-based (toxic) and Pt-based (costly) catalysts of alkane dehydrogenation, as reflected also in the increased number of reports related to the Zn-based catalysts in recent years. Here, we present a study of alumina-supported Zn-In and Zn-Mn propane dehydrogenation (PDH) catalysts prepared by the tailored methods. Specifically, the introduction of zinc relied on the chemical vapor deposition (CVD, using Zn vapor) onto alumina or alumina-supported indium or manganese materials, the latter two prepared by the impregnation of alumina with aqueous solutions of the respective metal nitrates followed by the calcination and hydrogen treatment. Alternatively, both zinc and indium were introduced by the co-impregnation of alumina with aqueous zinc and indium nitrates. The PDH tests revealed that the “dilution” of the active Zn2+ surface sites with In+ cations lead to a significant improvement in the catalytic performance, i.e., the introduction of In+ increased propene selectivity and attenuated the undesirable cracking and hydrogenolysis side reactions as well as decreased coke formation. In contrast, Mn2+ cations improved the catalytic properties of Zn2+ surface sites to a lesser extent than In+ cations. All prepared catalysts were characterized by DRIFT (diffuse reflectance infrared Fourier transform) spectroscopy of the adsorbed CO and H2 probe molecules. It was found that surface In+ and Mn2+ cations affect Zn2+ sites (electronic and geometric effect), which can be assessed from the position of the IR bands of zinc hydridespecies, formed due to the heterolytic hydrogen dissociation on the Zn2+ active sites. The effect of In and Mn dopants also was confirmed by the molecular DFT simulation.

Engineering of Thickness Tunable 2D Graphdiyne Film to ZnO Nanowalls via Nanospace‐Confined Synthesis Promotes NO2 Gas Sensing Performance

Achieving rapid response and recovery rates at low operating temperatures for NO2 is desirable for the application of sensors in industrial safety. In this study, we integrate a thickness tunable 2D graphdiyne (GDY) film into ZnO nanowalls (GDY/ZnO) via thermal evaporation of GDY, where ZnO nanowalls are used as the template to confine the growth space of the GDY film. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to reveal the transformation process of NO2. Ultraviolet photoemission spectroscopy (UPS) is utilized to analyze changes about the energy band of the materials. Density functional theory (DFT) calculations explain the reason for the selectivity of the samples to NO2. The scanning electron microscopy (SEM) results demonstrate that the thickness of the GDY film with a specific mesoporous structure (25‐53 nm) increases as the thermal evaporation temperature rises from 400 to 800°C.The representative ZG-600, synthesized with a thickness of 46 nm via thermal evaporation at 600°C, exhibits superior NO2 sensing performance. This is evidenced by its ultrahigh response (13.86, at 100 ppm and 150°C) and rapid response/recovery speeds (150 s/198 s), outperforming the ZnO sensor (198 s and 326 s). Moreover, it offers remarkable stability.

Exploiting the continuity equation for mechanistic understanding through spatially resolved SSITKA-DRIFTS: The role of carbonyls in RWGS over Pt/CeO2

Insight into mechanisms of heterogeneously catalyzed reactions holds importance in the development and optimization of new catalytic materials. Yet, the approaches often used in such investigations heavily rely on assumptions concerning the reactor and kinetics. Herein we report a new kind of kinetic investigation taking CO2 hydrogenation reaction, specifically the reverse water–gas shift (RWGS) reaction over 3 wt% Pt/CeO2, as an exemplifying case. The reported approach is based on spatially resolved steady-state isotopic transient kinetic analysis (SSITKA) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) identifying gaseous/surface species and their spatial variations along the reactor. This approach allows accurate evaluation of reaction mechanism by identifying correlations among the concentrations of gaseous/surface species and by quantitative description of their spatial variations by a kinetic model. Spatially resolved SSITKA-DRIFTS experiments show carbonate decomposition via a Pt-bound carbonyl to be the main route towards the production of carbon monoxide. Further kinetic modeling of the spatially resolved data confirms this mechanism proposal, and points to the production of water as the rate-limiting step.

DIFFUSE REFLECTANCE INFRARED FOURIER TRANSFORM SPECTROSCOPIC METHOD FOR ESTIMATION OF NERATINIB IN PHARMACEUTICALS: APPLICATION TO ANALYTICAL QUALITY BY DESIGN AND GREENNESS ASSESSMENT

In this research paper, we report an eco-friendly diffuse reflectance infrared fourier transform spectroscopic (DRIFTS) method for quantifying neratinib. The systematic method development was performed as per the recent analytical quality by design concept. The critical method variables such as resolution (cm-1) and the total number of scans were investigated using a central composite design to determine their influence on the measurements at 2204.64 cm-1. The method was valid over a linear (R2 > 0.99) range of 5-30 µg mg-1 of neratinib, with adequate accuracy (recovery > 100 %) and precision (RSD < 1%). Afterwards, the method greenness assessment was performed using the Analytical Greenness Metric and White Analytical Chemistry approach to establish the overall green sustainability of the current method. In a nutshell, the different functional groups of the drug were identified, and neratinib was quantified from the pharmaceutical tablets with optimum method robustness.

Heterogeneous reaction of NO2 with hematite: The effects of UV irradiation, O2 and relative humidity

Heterogeneous reactions on mineral dust surfaces are increasingly considered important in the removal of gaseous pollutants and the formation of secondary aerosols. Although the heterogeneous reaction of NO2 on the hematite surface has been investigated in many previous studies, little is known about the reaction of NO2 with hematite under ambient conditions. In this work, heterogeneous reactions of NO2 with hematite at 298 K were investigated via a coated-wall flow tube reactor and in situ diffuse reflectance Fourier transformed infrared spectroscopy (DRIFTS). The influence of UV illumination, relative humidity (RH) and O2 on the uptake coefficients and adsorption amount of NO2, as well as the nitrate formation on the hematite surface, has been analyzed comprehensively. UV irradiation shows a significant effect on the true uptake coefficient (γBET), which increases from 2.00 × 10−6 to 4.76 × 10−6 in the N2 stream and 1.32 × 10−6 to 4.07 × 10−6 in the air stream under dry conditions (∼0.3 % RH). RH (in the range of 0–67 %) exhibits an inhibitory effect on the adsorption of NO2 on the hematite surface because of the competition between NO2 and water molecules, that is, γBET and adsorption amount of NO2 decrease with an increase in RH under both the dark and light reaction conditions. Meanwhile, both the γBET and adsorption amount of NO2 on hematite decrease in the air stream compared to those in N2 conditions. In addition, the results from the DRIFTS experiments indicate that the presence of UV irradiation promotes the conversion of NO2 to nitrate and both the RH and O2 suppress the nitrate formation. From this research, the heterogeneous reactions between NO2 with mineral dust under ambient conditions will be better understood.

Morphologically tuned CuO-ZnO-CeO2 catalyst for CO2 hydrogenation to methanol.

Morphologically modified composite CuO-ZnO-CeO2 catalysts were synthesized using a single-step hydrothermal technique. The study highlights the influence of solvent on the structural and physico-chemical properties of the catalysts. Various techniques, such as XRD, FE-SEM, BET, XPS, and H2-TPR, were used to analyze the catalyst properties. Among the synthesized materials, the catalyst, prepared with a N,N-dimethyl formamide (DMF)-to-metal nitrates ratio of 20 (named as CZC-1), showed enhanced active sites in the form of surface features such as nanowire-like morphology, large surface area, low crystallite size, increased oxygen vacancies, and high CuO dispersion. A bench-scale fixed-bed flow reactor was used to examine the catalytic performance of the catalysts. At 225 °C reactor temperature, 30 bar reactor pressure, and with a space velocity of 6000 cm3 gcat-1 h-1, the CZC-1 catalyst showed 13.6% CO2 conversion and 74.1% methanol selectivity. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis confirmed the carbonate-formate-methoxy reaction pathway for methanol formation using the CZC-1 catalyst.

Mechanically treated Mn2O3 triggers peracetic acid activation for superior non-radical oxidation of micropollutants: Identification of reactive complexes

This study used a simple mechanical ball milling strategy to significantly improve the ability of Mn2O3 to activate peracetic acid (PAA) for sustainable and efficient degradation of organic micropollutant (like bisphenol A, BPA). BPA was successfully removed and detoxified via PAA activation by the bm-Mn2O3 within 30 min under neutral environment, with the BPA degradation kinetic rate improved by 3.4 times. Satisfactory BPA removal efficiency can still be achieved over a wide pH range, in actual water and after reuse of bm-Mn2O3 for four cycles. The change in hydrophilicity of Mn2O3 after ball milling evidently elevated the affinity of Mn2O3 for binding to PAA, while the reduction in particle size exposed more active sites contributing partially to catalytic oxidation. Further analysis revealed that BPA oxidation in the ball mill-treated Mn2O3 (bm-Mn2O3)/PAA process mainly depends on the bm-Mn2O3-PAA complex (i.e., Mn(III)−OO(O)CCH3) mediated non-radical pathway rather than R-O• and Mn(IV). Especially, the existence of the Mn(III)-PAA complex was definitely verified by in situ Raman spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Simultaneously, density functional theory calculations determined that PAA adsorbs readily on manganese sites thereby favoring the formation of Mn(III)−OO(O)CCH3 complexes. This study advances an in-depth understanding of the underlying mechanisms involved in the manganese oxide-catalyzed activation of PAA for superior non-radical oxidation of micropollutants.

Boosting photocatalytic NO oxidation mediated by high redox charge carriers from visible light-driven C3N4/UiO-67 S-scheme heterojunction photocatalyst

The construction of CN/UiO-67 (CNU) S-scheme heterojunction composites through in situ formation of UiO-67 on carbon nitride (C3N4) helps to address the limitations of carbon nitride (CN) in photocatalytic NO elimination. The optimized CNU3 demonstrates superior photocatalytic efficiency, which is attributed to electronic channels constructed by Zr-N bonds and S-scheme electron transport mechanism, effectively promoting the efficient separation of photogenerated charge carriers with high redox potentials. Density Functional Theory (DFT) calculations reveal redistributed electronic orbitals in CNU3, with progressive and continuous energy levels near the Fermi level, which bolsters electronic conduction. Comprehensive quenching experiments, Electron Paramagnetic Resonance (EPR), and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analyses highlight a synergistic interplay of electrons, holes, and superoxide radicals in CNU3, inhibiting the generation of toxic nitrogen oxide intermediates and culminating in highly efficient photocatalytic NO oxidation. This study not only elucidates the mechanisms underpinning the enhanced performance of CNU3 heterojunctions but also offers new perspectives on the preparation and interfacial charge separation of heterojunction photocatalysts.

A novel preparation of microporous nanosilica derived from aluminum-extracted residue of coal fly ash for highly selective CO2 adsorption

Currently, the poor adsorption performance caused by the unsatisfactory pore size seriously restricts the further development of microporous nanosilica (MS). Herein, an excellent microporous nanosilica was constructed by preparing calcium silicate hydrate (CSH) support from the aluminum-extracted residue of coal fly ash and modifying it with different activating agents (H2SO4, HNO3, HCl, CH3COOH, KOH, NaOH and Na2CO3). The results indicated that CH3COOH at 30 wt% was the optimal modifier, achieving a CO2 uptake of 1.42 mmol/g at 298 K and 1.0 bar. Then the effects of synthesis parameters including mass fraction, liquid–solid ratio, temperature, and time on the adsorption capacity of CO2 were further investigated. The obtained MSCp exhibited a high specific surface area (up to 505.71 m2/g), well-developed microporosity (0.085 cm3/g), and excellent CO2 uptake (2.12 mmol/g at 273 K, 1.41 mmol/g at 298 K). Based on the study of kinetics, isosteric heat of adsorption (Qst), and situ diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS), the adsorption mechanism of MSCp was determined to be mainly physical adsorption. Besides, the excellent CO2/CH4 selectivity of 20.91 (15/85, v/v) and 30.75 (50/50, v/v), CO2/N2 selectivity of 53.79 (15/85, v/v) and 163.76 (50/50, v/v) were obtained from MSCp at 298 K and 1.0 bar. Finally, the binary gas breakthrough experiments and eight adsorption–desorption cycles confirmed the MSCp was suitable for selective adsorption of CO2 in practical applications.

Irradiation induced mineral changes of NWA10580 meteorite determined by infrared analysis

Context. Identifying minerals on asteroid surfaces is difficult as space weathering modifies the minerals’ infrared spectra. This should be better understood for proper interpretation. Aims. We simulated the space weathering effects on a meteorite and recorded the alterations of the crystalline structure, such as the change in peak positions and full width at half maximum values. Methods. We used proton irradiation to simulate the effects of solar wind on a sample of NWA 10580 CO3 chondrite meteorites. After irradiation in three gradually increased steps with 1 keV ion energy, we used infrared microscopic reflectance and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to identify and understand the consequences of irradiation. Results. We find negative peak shifts after the first and second irradiations at pyroxene and feldspar minerals, similarly to the literature, and this shift was attributed to Mg loss. However, after the third irradiation a positive change in values in wavenumber emerged for silicates, which could come from the distortion of SiO4 tetrahedra, resembling shock deformation. The full width at half maximum values of major bands show a positive (increasing) trend after irradiations in the case of feldspars, using IR reflection measurements. Comparing DRIFTS and reflection infrared data, the peak positions of major mineral bands were at similar wavenumbers, but differences can be observed in minor bands. Conclusions. We measured the spectral changes of meteorite minerals after high doses of proton irradiation for several minerals. We show the first of these measurements for feldspars; previous works only presented pyroxene, olivine, and phyllosilicates.

Zr-Based MOF-545 Metal-Organic Framework Loaded with Highly Dispersed Small Size Ni Nanoparticles for CO2 Methanation.

We report the use of Zr-based metal-organic frameworks (MOFs) MOF-545 and MOF-545(Cu) as supports to prepare catalysts with uniformly and highly dispersed Ni nanoparticles (NPs) for CO2 hydrogenation into CH4. In the first step, we studied the MOF support under catalytic conditions using operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, ex situ characterizations (PXRD, XPS, TEM, and EDX-element mapping), and DFT calculations. We showed that the high-temperature conditions undoubtedly confer a potential for catalytic functionality to the solids toward CH4 production, while no role of the Cu could be evidenced. The MOF was shown to be transformed into a catalytically active material, amorphized but still structured with dehydroxylated Zr-oxoclusters, in line with DFT calculations. In the second step, Ni@MOF-545 catalysts were prepared using either impregnation (IM) or double solvent (DS) methods, followed by a dry reduction (R) route under H2 to immobilize Ni NPs. The highest catalytic activity was obtained with the Ni@MOF-545 DS R catalyst (595 mmolCH4 gNi-1 h-1) with 100% CH4 selectivity and 60% CO2 conversion after ∼3 h. The higher catalytic activity of Ni@MOF-545 DS R is a result of much smaller (∼5 nm) and better dispersed Ni NPs than in the IM sample (20-40 nm), the latter exhibiting sintering. The advantages of the encapsulation of Ni NPs by the DS method and of the use of a MOF-545-based support are discussed, highlighting the interest of designing yet-unexplored Zr-based MOFs loaded with Ni NPs for CO2 hydrogenation.

Photothermal catalytic C–C coupling to ethylene from CO2 with high efficiency by synergistic cooperation of oxygen vacancy and half-metallic WTe2

Photothermal catalytic CO2 conversion provides an effective solution targeting carbon neutrality by synergistic utilization of photon and heat. However, the C–C coupling initiated by photothermal catalysis is still a big challenge. Herein, a three-dimensional (3D) hierarchical W18O49/WTe2 hollow nanosphere is constructed through in-situ embodying of oxygen vacancy and tellurium on the scaffold of WO3. The light absorption towards near-infrared spectral region and CO2 adsorption are enhanced by the formation of half-metal WTe2 and the unique hierarchical hollow architecture. Combining with the generation of oxygen vacancy with strengthened CO2 capture, the photothermal effect on the samples can be sufficiently exploited for activating the CO2 molecules. In particular, the close contact between W18O49 and WTe2 largely promotes the photoinduced charge separation and mass transfer, and thus the *CHO intermediate formation and fixedness are facilitated. As a result, the C–C coupling can be evoked between tungsten and tellurium atoms on WTe2. The ethylene production by optimized W18O49/WTe2 reaches 147.6 μmol g−1 with the selectivity of 80%. The in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations are performed to unveil the presence and significance of aldehyde intermediate groups in C–C coupling. The half-metallic WTe2 cocatalyst proposes a new approach for efficient CO2 conversion with solar energy, and may especially create a new platform for the generation of multi-carbon products.

High-Capacity, Cooperative CO2 Capture in a Diamine-Appended Metal-Organic Framework through a Combined Chemisorptive and Physisorptive Mechanism.

Diamine-appended Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) metal-organic frameworks are promising candidates for carbon capture that exhibit exceptional selectivities and high capacities for CO2. To date, CO2 uptake in these materials has been shown to occur predominantly via a chemisorption mechanism involving CO2 insertion at the amine-appended metal sites, a mechanism that limits the capacity of the material to ∼1 equiv of CO2 per diamine. Herein, we report a new framework, pip2-Mg2(dobpdc) (pip2 = 1-(2-aminoethyl)piperidine), that exhibits two-step CO2 uptake and achieves an unusually high CO2 capacity approaching 1.5 CO2 per diamine at saturation. Analysis of variable-pressure CO2 uptake in the material using solid-state nuclear magnetic resonance (NMR) spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveals that pip2-Mg2(dobpdc) captures CO2 via an unprecedented mechanism involving the initial insertion of CO2 to form ammonium carbamate chains at half of the sites in the material, followed by tandem cooperative chemisorption and physisorption. Powder X-ray diffraction analysis, supported by van der Waals-corrected density functional theory, reveals that physisorbed CO2 occupies a pocket formed by adjacent ammonium carbamate chains and the linker. Based on breakthrough and extended cycling experiments, pip2-Mg2(dobpdc) exhibits exceptional performance for CO2 capture under conditions relevant to the separation of CO2 from landfill gas. More broadly, these results highlight new opportunities for the fundamental design of diamine-Mg2(dobpdc) materials with even higher capacities than those predicted based on CO2 chemisorption alone.