Carbon Dioxide Activation Research Articles

Efficacy of grape seed procyanidins for inhibiting denitrification varies by source, soil texture, and cropping history

Plant-derived denitrification inhibitors, such as procyanidins derived from grape seed extract (GSE), hold potential in mitigating nitrous oxide (N2O) emissions, a potent greenhouse gas and stratospheric ozone depleter. A deeper understanding of the effects of GSE – considering aspects like rate, source, application timing, storage, and interactions with soil properties and cropping histories – on denitrification inhibition remains elusive. We conducted a series of laboratory microcosm experiments to assess these effects using denitrification enzyme activity (DEA) and measurements of N2O and carbon dioxide (CO2) production rates under both anaerobic and aerobic conditions, soil inorganic nitrogen (N), and other major soil properties. Our results revealed that one commercial GSE brand (USP GSE) inhibited DEA, while another source was ineffective. Two non-procyanidin compounds in commercial GSE mixtures, tartaric acid and gallic acid, actually enhanced DEA. Inhibition efficiency of the USP GSE varied significantly across soils with differing crop histories and physical properties, exhibiting a positive dose-response in three out of the five soils examined. Greater efficiency was observed in sandy soils compared to silt loam soils and in soils with a history of continuous corn production as opposed to soybean. The GSE application timing relative to urea addition and a one-week room temperature storage had minor effects on denitrification inhibition. In corn-cultivated soil, co-application of GSE and urea reduced cumulative N2O production by 27 % compared to soils treated with urea alone. The CO2 production and nitrate levels remained largely unaffected by GSE application. These findings supported the potential of GSE as a soil amendment to reduce N2O emissions in corn-cultivated soils. However, challenges including purity of procyanidins, cost-effectiveness, and inconsistent performance under various systems warrant consideration for broader field applications.

Microwave-Assisted Fabrication of Fugus-Based Biocarbons for Malachite Green and NO2 Removal.

The aim of the current study was to produce biocarbons through the activation of carbon dioxide with the extraction residues of the fungus Inonotus obliquus. To achieve this goal, a microwave oven was used to apply three different activation temperatures: 500, 600, and 700 °C. Low-temperature nitrogen adsorption/desorption was employed to determine the elemental composition, acid-base properties, and textural parameters of the resulting carbon adsorbents. Subsequently, the produced biocarbons were evaluated for their efficiency in removing malachite green and NO2. The adsorbent obtained by activation of the precursor in 700 °C had a specific surface area of 743 m2/g. In the aqueous malachite green solution, the highest measured sorption capacity was 176 mg/g. Conversely, under dry conditions, the sorption capacity for NO2 on this biocarbon was 21.4 mg/g, and under wet conditions, it was 40.9 mg/g. According to the experimental findings, surface biocarbons had equal-energy active sites that interacted with the dye molecules. A pseudo-second-order kinetics model yielded the most accurate results, indicating that the adsorption of malachite green was driven by chemisorption. Additionally, the study demonstrates a clear correlation between the adsorption capacity of the biocarbons and the pH level of the solution, as it increases proportionately.

Nickel toxicity mitigation by supplementation of acetylcholine in wheat: Growth, photosynthetic and antioxidant activities

Influence of exogenous treatment of acetylcholine (ACh; 5 and 10 µM) was studied on the growth, photosynthesis and nitrate reductase activity in wheat under nickel (500 µM Ni) stress. Plant height, fresh and dry weight of shoot showed a decline of 36%, 23% and 40% respectively while as increased by 35%, 44% and 47% due to 10 µM ACh over control. Treatment of ACh, at both concentrations, alleviated the decline with obvious effects at higher (10 µM) concentrations. Treatment of ACh resulted in increased content of total chlorophylls, carotenoids and photosynthesis, intercellular carbon dioxide, transpiration and PSII activity, which were however significantly reduced by Ni stress. Exogenous application of ACh alleviated the Ni stress mediated decline in the activity of nitrate reductase. Wheat plants treated with Ni showed increased production of hydrogen peroxide resulting in increased lipid peroxidation and electrolyte leakage, however treatment of ACh reduced these parameters significantly reflecting in alleviation of oxidative damage. Activity of antioxidant enzymes assayed (SOD, CAT, APX, DHAR and GR) and the content of ascorbic acid and reduced glutathione increased significantly in ACh treated plants under normal and Ni stress. Activities of SOD, CAT, APX, DHAR and GR was increased by 162%, 108%, 70%, 107% and 87% respectively in Ni + 10 µM ACh treated plants. In addition, the content of phenols and flavonoids increased due to application of ACh. Content of nitrogen, potassium and calcium increased due to ACh and also alleviated the decline induced due to Ni stress while as the content of Ni was reduced in plants treated with ACh.

Removal of Methyl Red from Aqueous Solution Using Biochar Derived from Fennel Seeds

In this study, fennel (Foeniculum vulgare) seeds were used as a precursor to obtain carbon adsorbents through physical activation with carbon dioxide and chemical activation by impregnating the precursor with sodium carbonate. The physical activation involved the carbonization of the precursor at a temperature of 600 °C for 60 min and activation at a temperature of 800 °C for 30 min with carbon dioxide. Chemical activation included impregnation of the precursor with sodium carbonate at a mass ratio of a precursor to activator of 1:2. The mixture was activated in a nitrogen atmosphere with a flow rate at a temperature of 700 °C for 45 min. The resulting biochar samples were washed with 5% hydrochloric acid and subsequently rinsed with boiling distilled water. The biochar adsorbents were characterized using low-temperature nitrogen adsorption–desorption isotherms, Boehm titration, and pH measurements of their aqueous extracts. The specific surface area of the obtained adsorbents ranged from 89 to 345 m2/g. Biochar adsorbents exhibit a predominance of acidic groups over basic groups on their surfaces. The sorption capacities of the obtained samples towards an aqueous solution of methyl red range from 26 to 135 mg/g. Based on adsorption studies, it was found that the adsorption of the dye on the obtained biochar materials follows a pseudo-second-order model. The Freundlich isotherm best describes the studied process, indicating the formation of a multilayer of adsorbate on the adsorbent surface. The efficacy of adsorption in aqueous solutions of methyl red was found to increase with the elevation of the process temperature. Moreover, thermodynamic studies have shown that the adsorption process is spontaneous and endothermic. Consequently, this work provides a description of the physicochemical parameters of two biochars obtained by physical and chemical activation of a little-studied precursor—fennel seeds—and studies on their potential use as adsorbents for contaminants from the aqueous phase.

Active carbon monoliths from soft brown coal: A systematic study of their preparation, pore structure modification and characterization

High surface area active carbons in a ‘honeycomb monolith’ (HM) configuration can be prepared directly from soft brown coal by a novel approach. Kneading the coal into a plasticine consistency enables it to be extruded in HM form, then dried, carbonized and activated, retaining its structural integrity throughout these steps. Unlike higher rank coals, soft brown coal, which inherently contains relatively high oxygen functional group concentrations and high moisture contents, develops a strong H-bonding network during kneading. This opens the way to a novel and simpler method of preparing activated carbons in a monolith configuration. A systematic study was therefore conducted to evaluate the potential of these monoliths for being converted into higher value activated carbons by a low-cost process. Carbon honeycomb monoliths HMs from brown coal were modified by carbon dioxide (CO2) activation with a uniform domain size over a wider range of activation conditions (1–3 h, 750–950 °C) and the products were characterized by N2 adsorption (surface area and porosity), SEM, TEM, Raman spectroscopy, XPS and elemental analysis. The optimum conditions for development of porosity, aromaticity and a graphitizing structure were activation at 900 °C for 3 h. Interestingly, higher temperatures did not yield additional benefits. These materials should be useful in applications requiring highly ordered carbon.

Enhanced CO2 Reactive Capture and Conversion Using Aminothiolate Ligand-Metal Interface.

Metallic catalyst modification by organic ligands is an emerging catalyst design in enhancing the activity and selectivity of electrocatalytic carbon dioxide (CO2) reactive capture and reduction to value-added fuels. However, a lack of fundamental science on how these ligand-metal interfaces interact with CO2 and key intermediates under working conditions has resulted in a trial-and-error approach for experimental designs. With the aid of density functional theory calculations, we provided a comprehensive mechanism study of CO2 reduction to multicarbon products over aminothiolate-coated copper (Cu) catalysts. Our results indicate that the CO2 reduction performance was closely related to the alkyl chain length, ligand coverage, ligand configuration, and Cu facet. The aminothiolate ligand-Cu interface significantly promoted initial CO2 activation and lowered the activation barrier of carbon-carbon coupling through the organic (nitrogen (N)) and inorganic (Cu) interfacial active sites. Experimentally, the selectivity and partial current density of the multicarbon products over aminothiolate-coated Cu increased by 1.5-fold and 2-fold, respectively, as compared to the pristine Cu at -1.16 VRHE, consistent with our theoretical findings. This work highlights the promising strategy of designing the ligand-metal interface for CO2 reactive capture and conversion to multicarbon products.

Metal to non-metal sites of metallic sulfides switching products from CO to CH4 for photocatalytic CO2 reduction

The active center for the adsorption and activation of carbon dioxide plays a vital role in the conversion and product selectivity of photocatalytic CO2 reduction. Here, we find multiple metal sulfides CuInSnS4 octahedral nanocrystal with exposed (1 1 1) plane for the selectively photocatalytic CO2 reduction to methane. Still, the product is switched to carbon monoxide on the corresponding individual metal sulfides In2S3, SnS2, and Cu2S. Unlike the common metal or defects as active sites, the non-metal sulfur atom in CuInSnS4 is revealed to be the adsorption center for responding to the selectivity of CH4 products. The carbon atom of CO2 adsorbed on the electron-poor sulfur atom of CuInSnS4 is favorable for stabilizing the intermediates and thus promotes the conversion of CO2 to CH4. Both the activity and selectivity of CH4 products over the pristine CuInSnS4 nanocrystal can be further improved by the modification of with various co-catalysts to enhance the separation of the photogenerated charge carrier. This work provides a non-metal active site to determine the conversion and selectivity of photocatalytic CO2 reduction.

Donor-acceptor activation of Carbon Dioxide.

The activation and functionalization of carbon dioxide entails great interest related to its abundance, low toxicity and associated environmental problems. However, the inertness of CO2 has posed a challenge towards its efficient conversion to added-value products. In this review we discuss one of the strategies that have been widely used to capture and activate carbon dioxide, namely the use of donor-acceptor interactions by partnering a Lewis acidic and a Lewis basic fragment. This type of CO2 activation resembles that found in metalloenzymes, whose outstanding performance in catalytically transforming carbon dioxide encourages further bioinspired research. We have divided this review into three general sections based on the nature of the active sites: metal-free examples (mainly formed by frustrated Lewis pairs), main group-transition metal combinations, and transition metal heterobimetallic complexes. Overall, we discuss one hundred compounds that cooperatively activate carbon dioxide by donor-acceptor interactions, revealing a wide range of structural motifs.

New Insight into the Electronic Effect for Cu Porphyrin Catalysts in Electrocatalytic of CO2 into CH4.

Perturbation of the copper (Cu) active site by electron manipulation is a crucial factor in determining the activity and selectivity of electrochemical carbon dioxide (CO2 ) reduction reaction (e-CO2 RR) in Cu-based molecular catalysts. However, much ambiguity is present concerning their electronic structure-function relationships. Here, three molecular Cu-based porphyrin catalysts with different electron densities at the Cu active site, Cu tetrakis(4-methoxyphenyl)porphyrin (Cu─T(OMe)PP), Cu tetraphenylporphyrin (Cu─THPP), and Cu tetrakis(4-bromophenyl)porphyrin (Cu─TBrPP), are prepared. Although all three catalysts exhibit e-CO2 RR activity and the same reaction pathway, their performance is significantly affected by the electronic structure of the Cu site. Theoretical and experimental investigations verify that the conjugated effect of ─OCH3 and ─Br groups lowers the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbitals (LUMO) gap of Cu─T(OMe)PP and Cu─TBrPP, promoting faster electron transfer between Cu and CO2 , thereby improving their e-CO2 RR activity. Moreover, the high inductive effect of ─Br group reduces the electron density of Cu active site of Cu─TBrPP, facilitating the hydrolysis of the bound H2 O and thus creating a preferable local microenvironment, further enhancing the catalytic performance. This work provides new insights into the relationships between the substituent group characteristics with e-CO2 RR performance and is highly instructive for the design of efficient Cu-based e-CO2 RR electrocatalysts.

Halide-free squaramide–phenolate organocatalyst for the cycloaddition of CO2 into epoxides

The cycloaddition of CO2 into epoxide (CCE) reaction was the few routes viable industrially in catalytic fixation of carbon dioxide into value-added chemicals in which cocatalyst halide was predominant. To obviate the harmful corrosion of halide anions to steel reactors, and to alleviate the environmental burden of halogen waste, halide-free catalyst was desirable. We propose a category of one-component H-bond donor (HBD) and nucleophilic anion (HBD–anion) bifunctional organocatalyst as representative halide-free catalyst in CCE reactions. Squaramide (Sq) in conjugation with phenolate constitutes a typical HBD–anion catalyst featured with the squaramide as the HBD moiety and the phenolate as the nucleophilic anion moiety. Series of pre-catalyst in structure of squaramide–phenol (Sq–PhOH) was designed and the active catalyst Sq–phenolate (Sq–PhO) was generated from the corresponding Sq–PhOH by deprotonating of the weakly acidic hydroxyl of the phenol by super strong Brønsted base. In an optimal N-benzyl squaramide para-phenol (Sq–PhOH-p) and P2 phosphazene (t-BuP2) combination, CCE reactions proceed under mild conditions of 120 °C, and atmospheric pressure of 0.1 MPa, by 2.5 mol % loading of catalyst Sq–PhOH-p/t-BuP2. Terminal epoxides were transformed with excellent conversions (86–99 %) and high selectivity (85–97 %) in 8 h. Bifunctional activations mechanisms were proposed and validated. 1H and 13C NMR titrations certified the coordination of H-bond donor squaramide to epoxide, and FT-IR spectra observed formation of phenyl carbonate anion from phenolate and carbon dioxide, these suggested unprecedent CCE reaction composed capture of CO2 in carbonate anion followed by its intramolecular nucleophilic attack on the HBD coordinated epoxide as the key catalytic steps. The squaramide–phenolate catalytic dyad exemplified halide-free HBD–anion organocatalyst of wide scope for carbon dioxide activation and fixation.

Effect of Time on the Properties of Bio-Nanocomposite Films Based on Chitosan with Bio-Based Plasticizer Reinforced with Nanofiber Cellulose.

The deterioration of the performance of polysaccharide-based films over time, particularly their hydrophilicity and mechanical properties, is one of the main problems limiting their applications in the packaging industry. In the present study, we proposed to improve the performance of chitosan-based films through the use of: (1) nanocellulose as an additive to reduce their hydrophilic nature; (2) bio-based plasticizer to improve their mechanical properties; and (3) chestnut extract as an antimicrobial agent. To evaluate their stability over time, the properties of as-formed films (mechanical, hydrophilic, barrier and antibacterial) were studied immediately after preparation and after 7, 14 and 30 days. In addition, the morphological properties of the films were characterized by scanning electron microscopy, their structure by FTIR, their transparency by UV-Vis and their thermal properties by TGA. The films showed a hydrophobic character (contact angle above 100°), barrier properties to oxygen and carbon dioxide and strong antibacterial activity against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. Moreover, the use of nanofillers did not deteriorate the elongation at breaks or the thermal properties of the films, but their addition reduced the transparency. In addition, the results showed that the greatest change in film properties occurred within the first 7 days after sample preparation, after which the properties were found to stabilize.

Effect of Microwave-Assisted CO2 Pyrolysis on the Production of Activated Carbon from Confiscated Cigarettes

Confiscated cigarettes are a significant problem worldwide, and in Malaysia, the Royal Malaysian Customs Department (RMCD) Perlis had confiscated 1.5 billion sticks of cigarettes from 2016 to 2019 and the cost of disposal reached RM1.2 billion. Confiscated cigarettes are commonly disposed by incineration which can cause environmental pollution. In this study, the cigarette tobacco was converted into activated carbon (AC) via microwave-assisted CO2 pyrolysis. The tobacco was first carbonized at 300℃, followed by carbon dioxide (CO2) activation under microwave heating. The highest yield, 31% was obtained at 616W for 6 min. The BET surface area for tobacco, char and the best AC produced were 1.99, 1.21 and 1.69 m2/g, respectively. Response surface methodology (RSM) of dye removal from AC showed that the optimum condition with the best adsorption properties was achieved at 364 Watt for 2 minutes, which resulted in 87.4% removal of methylene blue (MB). Due to the low surface area, the capability of the AC to adsorb MB dye might be assisted by a diversified factors that contributes to the adsorption mechanism. Modelling of the adsorption data also showed that the adsorption process occurs in multilayers of the adsorbent, best fit to the Freundlich isotherm. Microwave-assisted CO2 pyrolysis shows potential in the production of AC from tobacco and could be further improved to increase the surface area.

Revealing CO2 dissociation pathways at vicinal copper (997) interfaces

Size- and shape-tailored copper (Cu) nanocrystals can offer vicinal planes for facile carbon dioxide (CO2) activation. Despite extensive reactivity benchmarks, a correlation between CO2 conversion and morphology structure has not yet been established at vicinal Cu interfaces. Herein, ambient pressure scanning tunneling microscopy reveals step-broken Cu nanocluster evolutions on the Cu(997) surface under 1 mbar CO2(g). The CO2 dissociation reaction produces carbon monoxide (CO) adsorbate and atomic oxygen (O) at Cu step-edges, inducing complicated restructuring of the Cu atoms to compensate for increased surface chemical potential energy at ambient pressure. The CO molecules bound at under-coordinated Cu atoms contribute to the reversible Cu clustering with the pressure gap effect, whereas the dissociated oxygen leads to irreversible Cu faceting geometries. Synchrotron-based ambient pressure X-ray photoelectron spectroscopy identifies the chemical binding energy changes in CO-Cu complexes, which proves the characterized real-space evidence for the step-broken Cu nanoclusters under CO(g) environments. Our in situ surface observations provide a more realistic insight into Cu nanocatalyst designs for efficient CO2 conversion to renewable energy sources during C1 chemical reactions.

Activation of carbon dioxide with surface oxygen vacancy of ceria catalyst: An insight from in-situ X-ray absorption near edge structure analysis

The concentrations of oxygen vacancy (Ov) and trivalent Ce ions (Ce3+) have been widely recognized as key reactivity descriptors to the CeO2-based catalysts. Nonetheless, the Ov and Ce3+ concentrations of CeO2-based catalysts are often determined by ex-situ characterizations without considering their interactions with reactants, a situation that is difficult to reflect their effective amounts participated in the catalytic process. In this study, a series of CeO2 catalysts with varied Ov and Ce3+ concentrations were prepared by a hydrothermal method followed by calcination at different temperatures. These CeO2 catalysts were characterized and assessed by the synthesis of dimethyl carbonate (DMC) from the reaction of CO2 and methanol. Using in-situ X-ray absorption spectroscopy without and with CO2 adsorption, the quantitative analysis of effective Ce3+ (associated with surface Ov) present in CeO2 catalysts for DMC synthesis is achieved. These results shed light on the critical role of surface Ov in CeO2 catalysts for non-reductive conversion of CO2 as well as the importance of in-situ characterizations for effective Ov and Ce3+ concentrations in CeO2 catalysts.

Enhanced hydrogen production and carbon-resistance in the dry reforming of methane over M−Ni/KIT-6 catalysts (M = Fe or Cu): Role of the promoters

The effects of iron and copper promoter on physicochemical properties of nickel supported on mesoporous silica were investigated. Furthermore, it was correlated to the methane dry reforming catalytic activity. The presence of these promoters played a key role in catalytic activity and stability. An addition of a small dosage of 0.1 wt% copper or iron led to a significant enhancement of in methane conversion. Moreover, the catalytic deactivation was two times slower than the pristine catalyst. The big performance improvement comes from a better interaction between nickel and the support and higher carbon dioxide activation in the presence of the promoters. The hydrogen production in the case of using a promoted catalyst was found more effective than the unpromoted. The study on catalyst deactivation revealed that the formation of coke was the main reason. The high carbon gasification obtained in 0.1 M−10Ni/KIT-6 (M = Fe or Cu) led to good removal of amorphous carbon and therefore, lengthened catalyst lifetime.

Simultaneous Activation of Carbon Dioxide and Epoxides to Produce Cyclic Carbonates by Cross‐linked Epoxy Resin Organocatalysts

AbstractThe development of efficient bifunctional organocatalysts for the catalytic conversion of CO2under mild conditions remains particularly challenging. Inspired by the synergistic mechanism of intramolecular Lewis acid‐base active sites, we report a series of bifunctional cross‐linked epoxy resin organocatalysts containing multiple active sites for the cycloaddition reaction of dilute CO2with epoxides. These catalysts exhibit high reactivity and product selectivity (10 examples, >99 %) for the cycloaddition reactions of a variety of epoxides and CO2, and surprisingly, epichlorohydrin (ECH), can be converted under ambient temperature and pressure (25 °C, 1.0 bar) without co‐catalysts.1H NMR,13C NMR,19F NMR and in situ IR studies suggest that the simultaneous and efficient activation of CO2and epoxides is responsible for the improved catalytic activity. Upon an insightful investigation of the catalytic mechanism, this protocol will contribute to the development of efficient and environmentally friendly metal‐free catalysts.

Carbon Dioxide and Water Activation by Niobium Trioxide Anions in the Gas Phase.

Transition metals are important in various industrial applications including catalysis. Due to the current concentration of CO2 in the atmosphere, various ways for its capture and utilization are investigated. Here, we study the activation of CO2 and H2O at [NbO3]- in the gas phase using a combination of infrared multiple photon dissociation spectroscopy and density functional theory calculations. In the experiments, Fourier-transform ion cyclotron resonance mass spectrometry is combined with tunable IR laser light provided by the intracavity free-electron laser FELICE or optical parametric oscillator-based table-top laser systems. We present spectra of [NbO3]-, [NbO2(OH)2]-, [NbO2(OH)2]-(H2O) and [NbO(OH)2(CO3)]- in the 240-4000 cm-1 range. The measured spectra and observed dissociation channels together with quantum chemical calculations confirm that upon interaction with a water molecule, [NbO3]- is transformed to [NbO2(OH)2]- via a barrierless reaction. Reaction of this product with CO2 leads to [NbO(OH)2(CO3)]- with the formation of a [CO3] moiety.

Oxovanadium(V)-Catalyzed Synthesis of Unsymmetrical Ureas by Activation of Carbon Dioxide under Ambient Pressure

Oxovanadium(V)-Catalyzed Synthesis of Unsymmetrical Ureas by Activation of Carbon Dioxide under Ambient Pressure

CeO2 Frustrated Lewis Pairs Improving CO2 and CH3OH Conversion to Monomethylcarbonate.

Frustrated Lewis pairs (FLPs), discovered in the last few decades for homogeneous catalysts and in the last few years also for heterogeneous catalysts, are stimulating the scientific community's interest for their potential in small-molecule activation. Nevertheless, how an FLP activates stable molecules such as CO2 is still undefined. Through a careful spectroscopic study, we here report the formation of FLPs over a highly defective CeO2 sample prepared by microwave-assisted synthesis. Carbon dioxide activation over FLP is shown to occur through a bidentate carbonate bridging the FLP and implying a Ce3+-to-CO2 charge transfer, thus enhancing its activation. Carbon dioxide reaction with methanol to form monomethylcarbonate is here employed to demonstrate active roles of FLP and, eventually, to propose a reaction mechanism clarifying the role of Ce3+ and oxygen vacancies.

ZnO with engineered surface defects as a competent photocatalyst for CO2 photoreduction into valuable fuels under simulated solar light irradiation

Photocatalysis is one of the eco-friendly methods in greenhouse gases abatement by utilizing renewable resources such as sunlight. This study examined defective ZnO nanoparticles that serve as carbon dioxide (CO2) adsorption and activation sites in photocatalytic reactions. The defective ZnO nanoparticles were synthesized via a facile precipitation-hydrothermal method by only controlling the concentration of NaOH as the precipitating agent. The rough surface of ZnO were formed due to the heating treatment, where it conveniently removed the attached inorganic molecules on ZnO surfaces. The roughness surface of ZnO was observed by using Transmission Electron Microscopy (TEM) analysis, in which the pores with bright spot can be observed. Additionally, the defects originating from oxygen vacancies (VO), zinc interstitials (Zni) and carbonates groups (CO32−) was successfully optimized over variation of NaOH concentrations proven by Photoluminescence (PL) and X-Ray Photoelectron Spectroscopy (XPS) analysis. Here, 1 : 4 ZnO exhibited the highest CH4 yield (1.3 ×10-1 µmol) and 3-fold production than commercial ZnO (4.8 × 10-2 µmol). The reusability of 1 : 4 ZnO was demonstrated by conducting 4 cycles of stability test, which revealed a robust photocatalyst of 7.7% performance reduction after 4th cycle. A schematic mechanism pertaining to the novel defective ZnO nanoparticles in CO2 photoreduction to valuable fuels was proposed in this study, which undoubtedly will contribute a positive effect to industry’s long-term sustainability.