Efficient CO2 Research Articles

Defect anchored single atomic Tin-nitrogen sites on graphene nanomesh for enhanced CO2 electroreduction to CO

Developing Sn, nitrogen-doped carbon catalysts (Sn-NC) for efficient CO2 electroreduction (CO2RR) to CO remains a great challenge. Here, we employed a defective hierarchical porous graphene nanomesh to anchor the single atomic tin-nitrogen sites (A-Sn-NGM) for effective CO2 electroreduction. The synthesized A-Sn-NGM typically showed remarkable CO2RR activity towards CO production, which achieved a maximum CO Faradaic efficiency (FECO) of 98.7 % and a turnover frequency of 5117.4 h−1 at a potential of −0.6 V (vs. RHE). Further analysis proves that the increased activity to CO production of A-Sn-NGM derives from the enlarged roughness and enhanced intrinsic activity. Density-functional theory (DFT) calculations indicate that the adjacent carbon defects anchored Sn-Nx coordination sites can markedly inhibit the competing hydrogen evolution reaction (HER) and lower the energy barrier for the formation of *COOH intermediates as compared to bulk Sn-Nx sites without carbon defects. This work provides a reliable method by engineering the carbon support to improve the CO2RR performance for single-atom catalysts.

Praseodymium orthovanadate-waste PET bottle derived sulfur doped carbon for efficient Z-scheme photocatalytic CO2 reduction

Escalating amounts of carbon dioxide (CO2) in the Earth's atmosphere are a major cause of climate change and its negative consequences, making it a global concern. The present work highlights the intersection of waste management, resource utilization, and climate change mitigation, showcasing the potential for an additional sustainable and circular economy. Synthesizing carbon from waste polyethylene terephthalate (PET) bottles is an eco-friendly approach. X-ray diffraction, Raman spectroscopic, scanning electron microscopic, tunnelling electron microscopic, infrared fourier transform spectroscopy (FTIR) and X-ray photoelectron spectroscopic results indicate the effective extraction of carbon doped with sulfur (S@C) and the successive formation of nanocomposite with PrVO4 (PrV/S@C). Superior photocatalytic activity was observed under visible light compared to UV light. PrV/S@C showed enhanced light-driven CO2 reduction compared to pristine materials and was found to evolve 39, 56, and 98 µmol h−1 g−1 of H2, CH4 and CO, respectively. The effect of reaction temperature was examined and optimized at 100 °C. The enhanced activity in PrV/S@C compared to PrV and S@C probably due to the increased surface area, conductivity and synergy. In-Situ Diffused reflectance (DRIFT-IR) and liquid chromatography mass spectroscopy (LC-MS) confirm the evolution of CO and CH4. The optical, photo/electrochemical, Scavenger studies, Electron spin resonance (ESR) and Mott-Schottky studies suggest the formation of a direct Z-scheme photoredox reaction in the presence of PrV/S@C and sacrificial gent. The reusability studies for 5 cycles indicate good stability with a slight deviation in structure and morphology of PrV/S@C, as observed in XRD and SEM. Tackling plastic pollution and generating value-added carbonaceous products through CO2 reduction is the twin application of the present work that has piqued the interest of several researchers in environmental remediation.

Step-by-step transfer of photoexcited electron in donor-acceptor-catalyst configuration covalent triazine framework for efficient photoreduction CO2 to formic acid

Covalent triazine frameworks (CTFs) have great potential for photocatalysis. However, the electron-hole recombination and the lack of efficient catalytic sites constrain the activity and selectivity. Herein, a novel design strategy of donor–acceptor-catalyst (D-A-C) configuration is proposed. This configuration enables the photoexcited electron undergoes stepwise transfer from donor unit to acceptor unit and ultimately reaches catalytic center, effectively inhibiting electron-hole recombination. The proof-of-concept model CTF-TT-Ir, in which thieno[3,2-b]thiophene (TT) serves as the donor unit, triazine as the acceptor unit, and Cp*Ir(bpy) (Ir) as the built-in catalytic site, was prepared for the photocatalytic reduction of CO2 to HCOOH. The stepwise transfer of photoexcited electrons in the ternary structure has been demonstrated through the in-situ XPS measurements and the theoretical calculations. Photoluminescence and photocurrent tests have indicated CTF-TT-Ir exhibits superior charge separation efficiency. Without additional photosensitizer and co-catalyst, the photocatalytic HCOOH yield rate of CTF-TT-Ir reached 245 μmol g−1h−1 (selectivity of 97 %).

Adjusting the phase transition time node of a solid–liquid biphasic solvent based on 2-amino-2-methyl-1-propanol for efficient CO2 capture: Insight into the regulatory effect of aminoethylethanolamine

Solid-liquid biphasic solvents (SLBSs) hold promise as energy-efficient candidates for CO2 capture. Nevertheless, the premature phase transition of current SLBSs leads to inopportune solid precipitation, posing operational challenges for the CO2 capture system. This study proposed a promising strategy that using aminoethylethanolamine (AEEA) as a regulator to fine-tune the phase transition time node of the 2-amino-2-methyl-1-propanol (AMP)/N-methylpyrrolidone (NMP) SLBS, enabling the phase transition to occur precisely as desired. Experimental results showed that the AEEA/AMP/NMP (A/A/N) SLBS exhibited tunable phase transition time nodes, modulated by the concentration of AEEA. Specifically, with the addition of 0.2 mol·L−1 AEEA, the CO2 loading associated with the phase transition increased significantly, from 0.19 to 0.54 mol·mol−1, approaching the saturation loading of 0.57 mol·mol−1. The delayed phase transition would facilitate the CO2 absorption operation. The regulatory mechanism of AEEA on the phase transition were thoroughly studied via 13C NMR and quantum calculations. AMP reacted with CO2 to produce AMPCOO− and AMPH+, which had a significantly stronger affinity for each other than for the solvent NMP, mediated by strong hydrogen bond interactions. Consequently, the continuous and fast aggregation of AMPCOO− and AMPH+ caused their swift precipitation from NMP. With the introduction of AEEA, the derived product AEEAH+(S)COO–(P) acted as a bridge-builder, connecting AMPCOO− or AMPH+ and NMP via hydrogen bonds, increasing the solubility of the AMP-derived products in NMP, thus effectively delaying the phase transition. Thermodynamic analysis revealed that the A/A/N SLBS exhibited a total regeneration energy consumption of 1.94 GJ·ton−1 CO2, representing a significant reduction of 48.9 % compared to that of 30 wt% MEA. This study provided a novel idea for designing SLBSs with controllable phase transition behavior, and offered a promising A/A/N SLBS for energy-efficient CO2 capture.

Synergistic effect between ohmic contacts and localized surface plasmon resonance for enhancing CO2 photoreduction of BiOBr

The fast recombination rate of photogenerated carrier and short electron lifetime are the main factors affecting the CO2 reduction performance of BiOBr (BOB). The utilization of ohmic contacts and the localised surface plasmon resonance (LSPR) effect of metals can effectively solve the above problems. However, one mean alone is not ideal for improving the photocatalytic performance of BOB. Therefore, in this work, we reduced the metal Bi to the surface of BOB in an attempt to form a synergistic effect of ohmic contact and LSPR effect. DFT calculations confirm the ohmic contact between Bi and BOB. Meanwhile, electrochemical tests show that Bi/BOB-2 has a higher photocurrent density (1.1 μA/cm2), suggesting that the ohmic contact achieves ultrafast electron transfer from BOB to Bi under light. While the UV–Vis diffuse reflectance spectroscopy results show resonance absorption peaks from the LSPR effect of Bi, the TRPL results show that Bi/BOB-2 has a longer τave (3.05 ns), implying that longer-lived hot electrons are generated on the Bi surface. The synergistic effect of the two contributes to the efficient CO2 to CO transition on the catalyst surface. As a result, Bi/BOB-2 exhibites a 4.37-fold higher CO generation rate (11.45 μmolg-1 h−1) than that of pure BOB (2.62 μmolg-1 h−1) under light. This study provides a new blueprint for the design of BiOBr-based materials for efficient photocatalytic reduction of CO2.

Metal Hydrogen-Bonded Organic Frameworks as Open Lewis Acid Catalysts for Two Types of CO2 Transformations.

Efficient and multiple CO2 utilization into high-value-added chemicals holds significant importance in carbon neutrality and industry production. However, most catalysis systems generally exhibit only one type of CO2 transformation with the efficiency to be improved. The restricted abundance of active catalytic sites or an inefficient utilization rate of these sites results in the constraint. Consequently, we designed and constructed two metal hydrogen-bonded organic frameworks (M-HOFs) {[M3(L3-)2(H2O)10]·2H2O}n (M = Co (1), Ni (2); L = 1-(4-carboxyphenyl)-1H-pyrazole-3,5-dicarboxylic acid) in this research. 1 and 2 are well-characterized, and both show excellent stability. The networks connected by multiple hydrogen bonds enhance the structural flexibility and create accessible Lewis acidic sites, promoting interactions between the substrates and catalytic centers. This enhancement facilitates efficient catalysis for two types of CO2 transformations, encompassing both cycloaddition reactions with epoxides and aziridines to afford cyclic carbonates and oxazolidinones. The catalytic activities (TON/TOF) are superior compared with those of most other catalysts. These heterogeneous catalysts still exhibited high performance after being reused several times. Mechanistic studies indicated intense interactions between the metal sites and substrates, demonstrating the reason for efficient catalysis. This marks the first instance on M-HOFs efficiently catalyzing two types of CO2 conversions, finding important significance for catalyst design and CO2 utilization.

Triazole-based COF tightly hugging ionic liquids through interactions of hydrogen bonds for enhanced atmospheric CO2 conversion

In the conversion of CO2 into green chemicals, efficient catalysts are urgently needed. Composite catalysts with ionic liquids (ILs) fixed to covalent organic frames (COFs) are considered as ideal materials. However, synthesizing composite materials by modifying ionic liquids on covalent organic frameworks encountered challenges related to the modification process and the easy detachment of functional groups. In this paper, a variety of multifunctional components were combined into composites to tailor catalysts ([TMGVBr]x@COFs) for cycloaddition reaction under mild atmospheric CO2 condition. In the strategy of in-situ encapsulation, triazole-based COF (TT-COF) tightly “hugged” the ionic liquids ([TMGH+][-O2MVIm+][Br-]) through the inductions of hydrogen bonds, resulting in excellent stability. Moreover, owing to the synergy between [TMGH+][-O2MVIm+][Br-] and TT-COF, [TMGVBr]10@COF achieved a good catalytic activity with 96.3 % yield in the cycloaddition reactions under atmospheric CO2, 100 °C and 10 h. Furthermore, the strong hydrogen bonds between ionic liquids and the framework of TT-COF ensured the [TMGVBr]10@COF catalyst’s good catalytic stability. There, a new idea was proposed for the efficient conversion atmospheric CO2 using designed heterogeneous catalysts.

Ethanol-assisted synthesis of a Ni single-atom catalyst with poriferous 3D framework for efficient cascade CO2 electroreduction

Ethanol-assisted synthesis of a Ni single-atom catalyst with poriferous 3D framework for efficient cascade CO2 electroreduction

Synergy between electron donor and steric hindrance in Alkylated-Piperazine absorbents for efficient CO2 capture

Piperazine (PZ) and its derivatives are currently regarded as novel amine absorbents for efficient CO2 capture. However, the in-depth investigation of CO2 capture and understanding of the structure–activity relationship in PZ-based absorbents are still lacking. In this study, we conducted a systematic investigation of CO2 capture within the alkylated PZ-based absorbents. The results demonstrated that the increased alkylation degree can promote CO2 absorption by enhancing the electron donor effect of the secondary amine group in PZ. In addition, the incorporated alkyl group in PZ-based absorbent improves the CO2 desorption process by enhancing the steric hindrance effect. Particularly, the synergy between electron donor and steric hindrance effects in isopropyl alkylated-PZ (IPPZ) enables it to present enhanced cyclic capacity and remarkably low regeneration energy consumption (2.36 GJ·t−1 CO2) for CO2 capture. The present study makes a valuable contribution towards the future design and development of highly efficient absorbents for CO2 capture.

Conversion of secondary aluminum dross into hierarchical carbonate-intercalated Mg-Al layered double hydroxide for efficient CO2 capture

This paper explores the preparation of hierarchical Mg-Al layered double hydroxide (LDH) from secondary aluminum dross waste for the first time. The aluminum content of the waste was initially extracted in the form of a sodium aluminate solution using a multistep wet chemical process. CO3-intercalated Mg-Al LDH was then prepared at pH values of 9 and 11 by adding magnesium chloride to a mixed solution of sodium aluminate and sodium carbonate. The X-ray diffraction (XRD) analysis revealed that a pure LDH structure could be formed at pH 11. The quantification of the XRD data revealed that the synthesized LDH had an interlayer spacing of 3.1 Å. The microstructural porosity was 0.76 cm3/g, and the specific surface area was 134 m2/g. The field emission scanning electron microscopy (FESEM) analysis revealed a hierarchical layered structure composed of flake-like particles in the microstructure. The elemental mapping of the synthesized LDH showed a proper distribution of Mg, Al, C, and O. The synthesized Mg-Al-CO3 LDH was then used for a study on CO2 capture. The CO2 capture experiments demonstrated that the amount of CO2 adsorption is influenced by temperature, gas pressure, adsorbent mass, and exposure duration. Investigating the effects of time and temperature revealed that a CO2 adsorption of 0.94 mmol/g can be achieved at a temperature of 25 °C during a 90-minute exposure period. Varying the gas pressure from 1 to 2.5 bar, while maintaining a constant temperature of 25 °C and an adsorbent mass of 1.5 g, resulted in an increase in CO2 adsorption from 1.7 to 2.3 mmol/g. Reusability tests showed that the LDH could maintain a satisfactory adsorption value of 0.84 mmol/g after 5 cycles, indicating its potential for repeated use.

Facile synthesis of polymer-derived K, Ti co-doped Li4SiO4-based sorbent for efficient and stable post-combustion CO2 capture

Li4SiO4-based sorbent has received considerable attention in the past decade due to its attractive intrinsic merits for post-combustion CO2 capture. To meet the practical applications, the development of Li4SiO4-based sorbent with more higher capture performances by an easy preparation route is desired. In this work, a facile and novel polymer-derived ceramic strategy (PDCs) was used to yield the high-performance Li4SiO4-based sorbent. The phase evolution and microstructure development of Li4SiO4 during the polymer-to-ceramic conversion were investigated. The CO2 capture performances of obtained Li4SiO4 sorbent were studied by comparing with other methods. To further improve its capture performances, Ti(EtO)4-K2CO3 were doped in Li4SiO4, and the enhancement mechanism was surveyed. Results indicate that high-purity Li4SiO4 sorbent with high adsorption properties can be prepared by PDCs route at 700 ℃, and it possessed similar synthesis and adsorption kinetics with the Li4SiO4 prepared by sol–gel method. The 5 mol% Ti doping exhibited a dual enhancement of adsorption capacity and cyclic stability for Li4SiO4 sorbent. Especially, due to the positive synergistic effect of the K, Ti co-doping, the obtained K/5TE-PDCs-Li4SiO4 sorbent showed ultra-high adsorption capacity (0.303 gCO2/gsorbent), ultra-fast adsorption rate (0.219 gCO2/(gsorbent·min)) and ultra-stable cycling performance at a low CO2 concentration (15 vol%). These efficient and stable CO2 capture performances prove the huge potential of polymer-derived K, Ti co-doped Li4SiO4-based sorbent for practical industrial applications.

Directly synthesized high-silica CHA zeolite for efficient CO2/N2 separation

Carbon dioxide capture is an effective method to mitigate climate change. Highly CO2-selective and highly moisture-resistant absorbent is essential for energy-efficient carbon capture by absorption. Herein, a highly CO2-selective and high-silica CHA zeolite in a pure lithium form (Li-SSZ-13) was synthesized using a direct synthesis method for the first time. The effects of gel n(SiO2)/n(Al2O3) ratio, gel n(SiO2)/n(Li2O) ratio and synthesis time on the crystallinity, yield, micropore volume and CO2 loading of the crystals were systematically investigated. The adsorption isotherms of CO2 and N2 were measured for directly synthesized Li-SSZ-13, conventional Na-SSZ-13 and ion-exchanged Li-Na-SSZ-13 zeolites. The dynamic breakthrough adsorption properties were measured for Li-SSZ-13 in comparison with Na-SSZ-13 and Li-Na-SSZ-13. The obtained Li-SSZ-13 exhibited a high CO2 adsorption capacity of 4.48 mmol/g and a high CO2/N2 IAST selectivity of 310 at 100 kPa and 273 K, which were 45.0% and 441% higher than Na-SSZ-13 zeolite, 24.8% and 179% higher than Li-Na-SSZ-13 zeolite, respectively. It suggests that directly synthesized Li-SSZ-13 zeolite has great potential for efficient CO2 capture from flue gas.

Facile Synthesis of Self-Supported Solid Amine Sorbents for Direct Air Capture.

Conventional usage of tetraethylenepentamine (TEPA) via being supported on porous solid materials for carbon capture is susceptible to oxidative degradation during regeneration cycles. This study reports a novel method to synthesize a TEPA based solid polymer for efficient CO2 removal via direct air capture (DAC). The polymer was obtained through epoxy-amine crosslinking reaction, leading to the transformation of liquid TEPA to a self-supported solid polymer. The synthesis was conducted under ambient conditions via a one-pot process with no waste products, which is aligned with green synthesis. The performance of the solid amine was evaluated in DAC under realistic conditions and compared with TEPA supported on SiO2 and zeolite 13X prepared through the conventional method. The solid TEPA amine exhibited a high CO2 uptake of 6.2 wt.% comparable to the conventional counterparts. More importantly, the solid TEPA amine demonstrated high resistance to oxidation during the accelerated ageing process at 80 °C in air for 24 h, whereas the two supported TEPA samples experienced severe degradation, with zeolite 13X supported TEPA incurring a reduction of 86.5 % in CO2 capturing capacity after the ageing. This work sheds light on the novel usage of TEPA as an efficient solid amine for practical DAC operation.

Development of bio-based lightweight and thermally insulated bricks: Efficient energy performance, thermal comfort, and CO2 emission of residential buildings in hot arid climates

This study explores the viability of using industrial wastewater sludge (IWWS), generated by the mycelium treatment of dyeing wastewater, for the fabrication of lightweight and thermally insulating bricks. The pulverized IWWS was used at various replacement ratios of 0, 5, 10, 15, and 20 wt% of clay. The mixture was subjected to firing temperatures of 700, 800, and 900 °C. The effect of applying IWWS to the brick characteristics is assessed through an examination of the physico-mechanical and thermal properties. The utilization of IWWS resulted in a significant enhancement in apparent porosity (34.4 %), cold water absorption (25.6 %), boiling water absorption (28.5 %), linear drying shrinkage (5.1 %), and linear firing shrinkage (7.9 %) using 20 % IWWS at 900 °C. Furthermore, the density, compressive strength, and thermal conductivity were reduced as the substitution IWWS ratio increased, reaching up to 1662.9 kg/m3, 11.56 MPa, and 0.198 W/m.K., respectively, using 20 wt% IWWS at 900 °C. The effect of fabricated fired bricks (FBs) on the thermal insulation, CO2 emissions, and energy consumption of residential buildings was tested. This is accomplished by using energy modeling tools, such as Honeybee, Ladybug, and Climate Studio (Grasshopper plugins), in addition to Galapagos for optimizing wall design. The suggested wall design is being used in a communal residential building located in two distinct climatic regions, namely Cairo in Egypt and Jazan in Saudi Arabia. According to the projected mean vote (PMV) and anticipated percentage of discontent (PPD) measures, the utilization of fabricated FBs as wall materials exhibits significant improvements in thermal comfort. Furthermore, they lead to a 6 % and 7 % drop in CO2 emissions in Cairo and Jazan cities, respectively, as well as a significant 38.8 % and 39 % reduction in energy consumption in Cairo and Jazan cities, respectively. Therefore, the use of fabricated FBs demonstrates itself as a feasible and environmentally friendly choice for building construction.

S-scheme charge transfer and photoinduced self-heating effect synergistically enhance the solar-driven CO2 reduction over Cs3Bi2Br9/Bi2S3 hybrid

Photothermocatalytic CO2 reduction, which harnesses the solar power to not only supply heat input but also generate charge carriers, represents an attractive and sustainable approach for solar-to-fuel conversion. Herein, an innovative Cs3Bi2Br9/Bi2S3 (CBB/Bi2S3) hybrid catalyst was elaborately designed by an electrostatic-driven self-assembling approach, which can achieve the effect of “kill two birds with one stone”. On the one hand, Bi2S3 functions as a photothermal material owing to its photoinduced self-heating effect, which elevates the temperature of the catalyst for accelerating the catalytic reaction. On the other hand, Bi2S3 synchronously boosts charge separation by forming an S-scheme heterojunction with CBB, as revealed by first-principle simulation and a series of experimental techniques. Remarkably, the developed CBB/Bi2S3 hybrid affords an impressive CO production rate (RCO = 153.82 μmol g−1h−1) without any extra heat input. The present study can provide some enlightening guidance for developing high-performance photothermal catalysts for efficient CO2 conversion.

Recent advances on surface modification of non-oxide photocatalysts towards efficient CO2 conversion

Recent advances on surface modification of non-oxide photocatalysts towards efficient CO2 conversion

Preparation of UiO-66 membrane through heterogeneous nucleation assisted growth strategy for efficient CO2 capture under humid conditions

Metal-organic frameworks (MOFs) have driven the development of polycrystalline membranes in the field of gas separation owing to the strong adsorption-desorption behavior and stable framework structure. However, the poor heterogeneous bonding ability between crystals and the substrate leads to the unsatisfactory gas separation as well as low stability of MOF membranes, especially in the humid environment. Herein, we prepared a thin and defect-free UiO-66 membrane by a crystal heterogeneous nucleation assisted growth strategy for efficient CO2/N2 separation. The addition of small amount of water in the precursor solution promoted the crystal nucleation process on the substrate surface. Meanwhile, the smooth PDMS interlayer guaranteed the heterogeneous well-intergrown of crystals into thin UiO-66 membranes, and provided a hydrophobic environment. Therefore, the dense UiO-66 membrane with a small thickness exhibited a high CO2 permeance (177.4 × 10−9 mol·m−2·s−1·Pa−1) with moderate CO2/N2 selectivity (24.3) under humid conditions. Furthermore, the prepared membrane demonstrated excellent renewable performance after dehumidification at high temperature, and maintained good hydrothermal stability during long-term operation under the humid environment. This work provides a new insight for the design of high-quality MOF membranes and promotes the development of MOF membranes in practical gas separation process.

Asymmetric aggregation enables red-light CO2 reduction with tunable activity and selectivity by intermolecular electronic coupling

Photocatalytic CO2 reduction to value-added chemicals is a promising way to simultaneously mitigate environmental and energy issues. Integrating low-energy red light harvesting, fast charge separation, and robust CO2 activation in a photosystem is a crucial prerequisite for highly efficient CO2 photoreduction but remains a huge challenge. Herein, we constructed an aggregated [Ru(2, 2'-bipyridine)3]Cl2 (denoted as Ru(bpy)3Cl2) photosystem. Various characterizations combining molecular dynamic simulations and theoretical calculations confirm that the electronic coupling between adjacent Ru(bpy)3Cl2 molecules can induce orbital hybridization, thus broadening the light absorption edge to the red light region. Meanwhile, the asymmetric aggregation of Ru(bpy)3Cl2 enables exciton dissociation and charge transfer through a dipole polarization effect. Significantly, this dipole polarization can also upshift the d-orbital of Ni catalytic centers, greatly strengthening the activation of CO2 and lowering the formation energy barrier of COOH* intermediates. Consequently, the apparent quantum yield (AQY) of aggregates for CO2-to-CO reduction reaches 4.2% at 610 nm, significantly higher than the AQYs of other reported photosystems at wavelengths ≥ 600 nm. More importantly, the catalytic efficiency and selectivity of CO2 reduction can be rationally tuned by controlling the aggregated degrees of Ru(bpy)3Cl2. This work highlights the key role of Ru(bpy)3Cl2 aggregation in prompting red-light harvesting and CO2 activation, which may help boost CO2 photoreduction efficiency from a fresh perspective.

Nanocrystalline sodium mordenite as an efficient low-concentration CO2 adsorbent

Systematic control of the crystal size and morphology of zeolites to enhance their CO2 adsorption performance is of great importance from both environmental and economic perspectives. Here we report the seeded synthesis of sodium mordenite (Na-MOR) with a Si/Al ratio of 4.9 and an average crystal length and width of 70 and 40 nm, respectively, using γ-aminobutyric acid as a crystal growth inhibitor in the absence of any organic structure-directing agent (OSDA). This nanozeolite shows an unprecedented CO2 capacity of 1.58 mmol g−1 under dynamic direct air capture (DAC) conditions at 25 °C, which is approximately 40 % greater than the value (1.15 mmol g−1) of the best zeolite adsorbent (an unidentified OSDA-directed Na-MOR (Si/Al = 5.0) zeolite with Na+ enrichment in 8-ring side pockets), mainly due to its nanocrystalline nature. It has also been characterized by much faster CO2 adsorption kinetics (ca. 5 vs. 50 min equilibration time) compared to a commercial Na-MOR zeolite with Si/Al = 5.0. Our study paves the way for developing a more efficient zeolite-based DAC adsorbent.

Facile synthesis of benzimidazole based mono- and bimetallic zeolitic imidazole frameworks for enhanced CO2 capture performance

Utilization of Zeolite imidazole frameworks (ZIFs) based membrane for Efficient CO2 capture is one of the most significant and advantageous methods to reduce the greenhouse gas quantity in the atmosphere. Here we report a simple room temperature synthesis of robust monometallic ZIF-7, ZIF-9 and bimetallic Zn2+ and Co2+ containing ZIFs to achieve five porous meterials, Zn100−xCox-ZIF (X = 0, 25, 50, 75 and 100). All the synthesized ZIFs are characterized through powder X-ray diffraction, thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) to examine the phase, texture, morphology, chemical state and surface area. The presence of metal in a specific ratio was examined through the Energy Dispersive X-ray Spectrometer (EDS). Incorporation of Cobalt into Zn containing ZIFs not only increases their thermal stability but also enhances their photophysical properties, thereby decreasing the optical band gap. Furthermore, bimetallic ZIFs exhibited higher specific surface area and CO2 uptake capacity than their parents monometallic counterparts. Specific surface area and CO2 uptake capacity of mono/ bimetallic ZIFs were studied at 298 K. The CO2 uptake of 1.83 cm3/g, 4.76 cm3/g, 6.26 cm3/g, 9.62 cm3/g, and 16.62 cm3/g for ZIF-7, ZIF-9, Zn100−xCox-ZIF (X = 25, 50 and 75), respectively, are obtained.