CO2 Reduction Research Articles

Construction of biochar assisted S-scheme of CeO2/g-C3N4 with enhanced photoreduction CO2 to CO activity and selectivity

The multi-interface contacted S-scheme photocatalyst was used for CO2 reduction in this research. A hybrid nanostructures catalyst was constructed using g-C3N4 nanosheet, oxidized CeO2 nanoparticles, and biochar (BIO, cattail-derived). The g-C3N4-BIO/CeO2 catalyst exhibited high selectivity (> 95 %) in converting CO2 to CO in a gas-solid-liquid phase CO2 reduction system. Theoretical and experimental evidence suggests that the multi-interface and interfacial internal electric field (IEF) play a crucial role in enhancing electron transfer and redox ability in CO2 reduction processes. Ce4+ species in CeO2 have the capability to donate two electrons, facilitating the two-electron reduction process involved in the transformation of CO2 to CO. Additionally, Ce4+ in CeO2 acted as an electron trapping agent and could be reduced to Ce3+ ion after trapping electrons, which facilitated the separation process of photogenerated carriers inside CeO2. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrated that COOH* intermediate played a key role as the rate determining step in the overall CO2 photoreduction to CO. This investigation will contribute to the development and application of new and environmentally friendly BIO-based S-scheme photocatalysts.

Atomically dispersed nickel-bismuth dual-atom sites for high rate electrochemical CO2 reduction

We report a diatomic-site catalyst configuration constituted by Ni-N3 and Bi-N4 embedded in ultrathin nitrogenated carbon nanosheets (Ni/Bi-N-C) which showed dramatically improved activity and selectivity for the conversion of CO2 to CO. Specifically, the catalyst exhibited high CO Faradaic efficiency (FECO) of above 90 % over a wide potential window from −0.76 to −2.22 versus reversible hydrogen electrode with the maximum CO partial current density up to 312 mA cm−2 in a flow cell, and coupled with robust durability. Ni/Bi-N-C-based membrane electrode assembly (MEA) device presented ultrahigh FECO of 95.7 % at 750 mA and over 100 h of continuous operation without decay under constant current density of 100 mA cm−2. Mechanistic studies and density functional theory calculations reveal that regulating the CO2RR catalytic performance via nearby Ni and Bi active sites can potentially break the activity benchmark of the single metal counterparts because the neighboring Ni and Bi active sites work in synergy to decrease the reaction barrier for the formation of *COOH and desorption of *CO. This work presents an efficient combination of two metal atomic sites which was designed by optimizing the interaction between the atomic sites and key reaction intermediates, resulting in the high-rate electrocatalytic CO2 reduction.

Improving CO2 electroconversion by customizing the hydroxyl microenvironment around a semi-open Co-N2O2 configuration

Constructing local microenvironments is one of the important strategies to improve the electrocatalytic performances, such as in electrochemical CO2 reduction (ECR). However, effectively customizing these microenvironments remains a significant challenge. Herein, utilizing carbon nanotube (CNT) heterostructured semi-open Co-N2O2 catalytic configurations (Co-salophen), we have demonstrated the role of the local microenvironment on promoting ECR through regulating the location of hydroxyl groups. Concretely, compared with the maximum Faradaic efficiency (FE) of 62% for carbon monoxide (CO) presented by Co-salophen/CNT without a hydroxyl microenvironment, the designed Co-salophen-OH3/CNT, featuring hydroxyl groups at the Co-N2O2 structural opening, shows remarkable CO2-to-CO electroreduction activity across a wide potential window, with the FE of CO up to 95%. In particular, through the deuterium kinetic isotope experiments and theoretical calculations, we decoded that the hydroxyl groups act as a proton relay station, promoting the efficient transfer of protons to the Co-N2O2 active sites. The finding demonstrates a promising molecular design strategy for enhancing electrocatalysis.

Chemically bonded to construct S-scheme CNQDs/Bi2WO6 heterostructure: The Bi-N bonds as interfacial electronic channel boosting the efficient photocatalytic CO2 reduction under simulated sunlight

Photoinduced carrier separation efficiency plays a crucial role in determining the photocatalytic activity of photocatalysts, but it remains a challenge to accurately and efficiently control charge separation. Hence, we successfully prepared S-scheme CNQDs/Bi2WO6 heterostructure via a simple hydrothermal method. The theoretical calculations demonstrate that Bi-N bonds at the interface between CNQDs and Bi2WO6 serve as an electron transfer channel to facilitate charge transfer at the atomic level, which plays a vital role in driving the photoreduction of CO2 to CO. Interestingly, S-scheme heterostructure not only remains strong reducing ability of CNQDs, but also significantly reduces the energy barrier of *CO2 *COOH and release the product CO easily. The CO yield of the CNQDs/Bi2WO6 sample (26.24 µmol/g) was 11 times higher than that of the pure Bi2WO6 (2.43 µmol/g) without any sacrificial agents under 300 W xenon lamp. This work highlights the critical role of chemical bonding interfaces in the design of efficient S-scheme heterostructure photocatalysts.

Carbon Emission Accounting and Reduction Evaluation in Sponge City Residential Areas

This paper aims to establish a more standardized and regulated carbon emission accounting model for sponge cities by unifying the accounting content for carbon emissions and clarifying the relationships between carbon reduction benefits, carbon reduction effects, and carbon sequestration, in order to evaluate the carbon reduction outcomes and mechanisms of sponge city construction. Based on a Life Cycle Assessment (LCA) carbon emission accounting model using the carbon emission factor method, a newly constructed residential area in Tianshui City, Gansu Province, was selected as a case study, and the carbon emission reduction effect of sponge city construction was then investigated. Results indicated that the 30-year full life cycle carbon emissions for sponge city construction in the newly constructed residential area amounted to 828.98 tons, compared to 744.28 tons of CO2 reduction in traditional construction, representing a 47.31% reduction in carbon emissions. Over a 30-year life cycle, this equated to a total carbon emission reduction effect of 1460.31 tons. Additionally, under various rainfall scenarios in a typical year, the carbon emission reduction effect of sponge city construction exceeded the carbon emissions, achieving carbon neutrality within 22 to 30 years of operation. This demonstrates that the carbon emission reduction effect of sponge city communities is significant. The findings of this study provide data and a theoretical basis for the low-carbon construction of sponge cities in China.

Borohydride Compounds Catalyze the Selective 4e- Reduction of CO2 with 9-BBN.

The selective double hydroboration of CO2 into bis(boryl)acetal (BBA) is a challenging yet appealing reduction process since BBA can be used as a versatile C1 and Cn sources for the synthesis of value-added products. In the present study, we demonstrate that simple borohydride compounds are efficient and selective catalysts for the synthesis of BBA when using 9-borabicyclo(3.3.1)nonane (9-BBN) as a reductant. The experimental and theoretical investigations show that while the borohydride species catalyzes the first reduction step of CO2 into formoxyborane (2e- reduction intermediate), the observed 4e- reduction selectivity is mostly due to the ability of 9-BBN to reduce the formoxyborane into BBA without a catalyst. Notably, 0.2 mol % of LiH2BBN catalyzed the hydroboration of CO2 with 9-BBN as a reductant into the corresponding BBA in 77% yield with TON and TOF of 385 and 196 h-1, respectively. The simplicity of borohydride contrasts with the more elaborate catalytic systems used so far for the 4e- reduction of CO2.

Mechanistic insights into C-C coupling in electrocatalytic CO2 reduction reaction.

The utilization of CO2 has become an emerging area of research in response to climate change and global warming. The electrochemical CO2 reduction reaction (CO2RR) holds significant promise as a technology to address this issue by converting CO2 molecules into various commercially valuable chemicals. While CO2RR to C1 hydrocarbons has achieved high activity and selectivity, the C-C coupling to produce higher hydrocarbons remains challenging due to low energy efficiency and the prevalent hydrogen evolution reaction (HER) on the same catalyst, leading to high hydrogenation rates. In this review, we aim to elucidate the fundamental challenges of C-C coupling and explore potential strategies to enhance the selectivity for higher hydrocarbon products. We discuss the mechanisms underlying the formation of C2 and C3 products, focusing on molecular catalysts that facilitate C-C coupling by positioning CO2 molecules in close proximity. Additionally, we provide a comprehensive overview of different approaches to improve higher hydrocarbon selectivity, along with future suggestions and recommendations for new researchers in the field. This review serves as a valuable resource for both academic researchers and industrial stakeholders aiming for the commercialization of CO2RR technologies.

Techno-economic analysis of geothermal combined with direct and biomass-based carbon dioxide removal for high-temperature hydrothermal systems

Limiting global temperature rise to between 1.5 and 2 °C will likely require widespread deployment of carbon dioxide removal (CDR) to offset sectors with hard-to-abate emissions. As financial resources for decarbonization are finite, strategic deployment of CDR technologies is essential for maximizing atmospheric CO2 reductions. Carbon capture and sequestration (CCS), using either direct air capture (DACCS) or bioenergy (BECCS) technologies has a particular synergy with geothermal electricity generation. This is because expensive geothermal infrastructure can be leveraged to transport dissolved CO2 for storage in subsurface reservoirs.Here, we present a techno-economic comparison of renewable electricity generation coupled with either BECCS or DACCS at high-temperature, low-gas hydrothermal systems. We use a systems model that quantifies energy, carbon and financial flows through a generic hybrid power plant. At a CO2 market price of $100/tonne, the geothermal-BECCS system has a lower median cost of electricity generation ($88/MWh) than geothermal-DACCS ($181/MWh) and conventional geothermal ($89/MWh).Geothermal-BECCS also had the lowest costs of overall emissions abatement, $122/tCO2, accounting for carbon removal and assuming displacement of fossil-fuel generation. Abatement costs are even lower, $45/tCO2, for BECCS retrofit of existing geothermal plants, owing to discounted costs of pre-existing injection wells, steam fields, and plant equipment.For a case study based on a geothermal field in New Zealand's Taupō Volcanic Zone (TVZ), we determined that achieving CDR rates of 1 MtCO2/year via new geothermal-BECCS builds would require 62 standard geothermal wells and 790 kt/year of feedstock and result in 511 MWe in installed capacity. In contrast, geothermal-DACCS would need 49 wells and no external fuel source to achieve 1 MtCO2/year scale but result in only 190 MWe in installed capacity. Both pathways are calculated to require similar upfront investment costs at $2.2 billion and $2.3 billion for geothermal-BECCS and geothermal-DACCS respectively.Although geothermal-DACCS removes CO2 at high rates, its high parasitic load increases the overall decarbonization cost ($187/tCO2). In contrast, when biomass hybridization is considered, geothermal-BECCS has a lower cost of emissions abatement and produces 20 % more electricity than the benchmark geothermal plant. We conclude that this increase in electricity production makes geothermal-BECCS the more cost-effective geothermal-based CDR configuration. Finally, we argue that revenues from net-negative CO2 emissions and increased power production make geothermal-CDR a cost-competitive decarbonization technology.

Identification of Degradation Reasons for a CO2 MEA Electrolyzer Using the Distribution of Relaxation Times Analysis.

The application of membrane electrode assembly (MEA) in electrocatalytic CO2 reduction (ECO2R) technology is an essential step toward industrialization. Nevertheless, the issue of ECO2R failure in MEA during extended operation hinders its industrial application. In this work, we employed in situ, nondestructive electrochemical impedance spectroscopy (EIS) techniques combined with distribution of relaxation times (DRT) methodology to diagnose the causes of the failure. By systematically investigating the variations in polarization resistance throughout the degradation process and utilizing a controlled variable approach to identify the origin of polarization, we diagnosed the degeneration of ionomers as the primary cause of the performance degradation of ECO2R in this instance. We further confirmed the reliability of our findings through material characterization and respraying ionomers onto the catalyst surface. This research provides an effective diagnostic method for the failure analysis of ECO2R performance in MEA, which is crucial for advancing industrialization of ECO2R technology.

Tuning the interfacial reaction environment via pH-dependent and induced ions to understand C–N bonds coupling performance in NO3− integrated CO2 reduction to carbon and nitrogen compounds over dual Cu-based N-doped carbon catalyst

Dual atomic catalysts (DAC), particularly copper (Cu2)-based nitrogen (N) doped graphene, show great potential to effectively convert CO2 and nitrate (NO3−) into important industrial chemicals such as ethylene, glycol, acetamide, and urea through an efficient catalytical process that involves C–C and C–N coupling. However, the origin of the coupling activity remained unclear, which substantially hinders the rational design of Cu-based catalysts for the N-integrated CO2 reduction reaction (CO2RR). To address this challenge, this work performed advanced density functional theory calculations incorporating explicit solvation based on a Cu2-based N-doped carbon (Cu2N6C10) catalyst for CO2RR. These calculations are aimed to gain insight into the reaction mechanisms for the synthesis of ethylene, acetamide, and urea via coupling in the interfacial reaction micro-environment. Due to the sluggishness of CO2, the formation of a solvation electric layer by anions (F−, Cl−, Br−, and I−) and cations (Na+, Mg2+, K+, and Ca2+) leads to electron transfer towards the Cu surface. This process significantly accelerates the reduction of CO2. These results reveal that *CO intermediates play a pivotal role in N-integrated CO2RR. Remarkably, the Cu2-based N-doped carbon catalyst examined in this study has demonstrated the most potential for C–N coupling to date. Our findings reveal that through the process of a condensation reaction between *CO and NH2OH for urea synthesis, *NO3− is reduced to *NH3, and *CO2 to *CCO at dual Cu atom sites. This dual-site reduction facilitates the synthesis of acetamide through a nucleophilic reaction between NH3 and the ketene intermediate. Furthermore, we found that the I− and Mg2+ ions, influenced by pH, were highly effective for acetamide and ammonia synthesis, except when F− and Ca2+ were present. Furthermore, the mechanisms of C–N bond formation were investigated via ab-initio molecular dynamics simulations, and we found that adjusting the micro-environment can change the dominant side reaction, shifting from hydrogen production in acidic conditions to water reduction in alkaline ones. This study introduces a novel approach using ion-H2O cages to significantly enhance the efficiency of C–N coupling reactions.

Characterizing hydrogen-diesel dual-fuel performance and emissions in a commercial heavy-duty diesel truck

This study investigates hydrogen (H2) as a supplementary fuel in heavy-duty diesel engines using pre-manifold injection. A H2-diesel dual-fuel (H2DF) system was implemented on a commercial class-8 heavy-duty diesel truck without modifying the original diesel injection system and engine control unit (ECU). Tests were conducted on a chassis dynamometer at engine speeds between 1000-1400rpm with driver-demanded torques from 10-75%. The hydrogen energy fraction (HEF) was strategically controlled in the range between 10-30%. Overall, CO2 reduction (comparable to the HEF level) was achieved with similar brake-specific energy consumption (BSEC) at all loads and speeds. To maintain the same shaft torque, the driver demanded torque was reduced in H2DF operation, which resulted in a lower boost pressure. At higher loads, engine-out BSNOx slightly decreased, while BSCO and black carbon (BC) increased significantly due to lower oxygen concentration resulting from the lower boost pressure. At lower loads, engine-out BSCO and BSBC decreased moderately, while NO2/NO ratio increased substantially in H2DF operation. Deliberate air path and diesel injection control are expected to enable higher HEF and GHG reductions.

Potential-driven structural distortion in cobalt phthalocyanine for electrocatalytic CO2/CO reduction towards methanol

Cobalt phthalocyanine immobilized on carbon nanotube has demonstrated appreciable selectivity and activity for methanol synthesis in electrocatalytic CO2/CO reduction. However, discrepancies in methanol production selectivity and activity between CO2 and CO reduction have been observed, leading to inconclusive mechanisms for methanol production in this system. Here, we discover that the interaction between cobalt phthalocyanine molecules and defects on carbon nanotube substrate plays a key role in methanol production during CO2/CO electroreduction. Through detailed operando X-ray absorption and infrared spectroscopies, we find that upon application of cathodic potential, this interaction induces the transformation of the planar CoN4 center in cobalt phthalocyanine to an out-of-plane distorted configuration. Consequently, this potential induced structural change promotes the transformation of linearly bonded *CO at the CoN4 center to bridge *CO, thereby facilitating methanol production. Overall, these comprehensive mechanistic investigations and the outstanding performance (methanol partial current density over 150 mA cm−2) provide valuable insights in guiding the activity and selectivity of immobilized cobalt phthalocyanine for methanol production in CO2/CO reduction.

Z-scheme heterojunction enhanced photocatalytic performance for CO2 reduction to CH4.

Due to the high charge separation efficiency leading to high photocatalytic activity, there has been significant interest in enhancing the charge separation ability of photocatalysts by controlling the heterojunction structure. To investigate the effect of the heterojunction structure on the photocatalytic performance of composite catalysts and understand its corresponding mechanism, a Z-scheme ZnFe2O4/ZnO/CdS heterojunction was constructed using the ultrasound method and used for CO2 photoreduction. The Z-scheme heterojunction catalyst demonstrates elevated photocatalytic and charge separation efficiencies. Specifically, the conversion rate for the photocatalytic conversion of CO2 to CH4 reaches 105.9 μmol g-1 h-1, surpassing that of the majority of previously reported semiconductor photocatalysts like ZnFe2O4/CdS. This research offers a fresh perspective on the development of innovative heterojunction photocatalysts and broadens the utilization of ternary composite materials in CO2 photoreduction.

Coke breeze combustion and emission behaviors of CO and NO during iron ore sintering

CO emission reduction, especially the coordinated emission reduction of CO and NO in sintering flue gas, has attracted widespread attention in the world. The effects of different sintering raw materials, temperature and atmosphere on coke breeze combustion and CO and NO emission behaviors were studied. The results show that, sintering raw materials significantly improved the combustion performance of coke breeze, and promoted the simultaneous reduction of CO and NO emissions. Among them, Dolomite had the strongest catalytic effect, which reduced the apparent activation energy of coke breeze combustion reaction from 99.35 kJ/mol to 56.11 kJ/mol, and the emission reductions of CO and NO were as high as 47.84 % and 73.25 %, respectively. The catalytic ability of the raw materials components was CaO ＞ MgO ＞ Fe2O3. However, during the combustion process of coke breeze without raw materials, the reduction of NO by CO was affected by the atmosphere of the boundary layer, the conversion of N element was negatively correlated with the content of CO. When the temperature increased from 600 ℃ to 1 050 ℃, the combustion performance was improved, the thickness of the combustion zone was reduced by 47.92 %, the total emission of CO was decreased by 65.39 %, and the total emission of NO was increased by 23.05 %. The O2 concentration decreased from 21 % to 10 %, the combustion rate decreased, the combustion zone thickened by 90 %, incomplete combustion was promoted, the total emission of CO increased by 101.15 %, and NO decreased by 21.09 %. The CO2 concentration increased from 5 % to 15 %, the gasification reaction was enhanced, the combustion time was extended, the combustion zone thickened by 45.9 %, the total emission of CO increased by 87.12 %, and the reducing atmosphere was enhanced, which was conductive to the reduction of NO by CO, and the total emission of NO decreased by 50.59 %.

Synergistic effect between sulfur vacancies and S-scheme heterojunctions in WO3/VS-Zn3In2S6 for enhanced photocatalytic CO2 reduction in H2O vapor

Converting CO2 into CO, CH4, and other hydrocarbons using solar energy presents a viable approach for addressing energy shortages. In this study, photocatalysts with S-deficient WO3/Zn3In2S6 (WO3/VS-ZIS) S-scheme heterojunctions have been successfully synthesized. Under UV–vis light irradiation, 20 %WO3/VS-ZIS demonstrated significantly improved CO2 reduction activity and CH4 selectivity. Detailed characterization and density functional theory (DFT) calculations reveal that the enhanced performance is due to the synergistic optimization of the S-scheme heterojunction and sulfur vacancies (VS) for CO2 reduction. The presence of VS aids in the adsorption and activation of CO2 and enhances the separation of charge carriers. The 2D/2D S-scheme heterostructure assembled with WO3 nanosheets not only accelerates the migration and separation of photoexcited charge carriers but also improves the adsorption of H2O and the formation of VS, thereby increasing the adsorption and activation of CO2 and facilitating the protonation of CO* to produce CH4. This study clarifies the synergistic effect of VS and S-scheme heterostructures in improving photocatalytic performance, offering valuable insights into the photoactivation process of CO2 at VS in S-scheme heterojunctions.

Tuning Rigid Polyurethane Foam with Eco-friendly Cellulose Nanocrystals from Oil Palm Empty Fruit Bunches as Energy-Efficient Material Composites for Buildings

The development of novel materials based on renewable materials with beneficial properties that assist with energy efficiency and conservation has been encouraged by increasing consciousness of environmental issues. This research intends to use sustainable cellulose nanocrystals (CNC) obtained from oil palm empty fruit bunches (OPEFB) as reinforcement to enhance the properties of rigid polyurethane foam (RPUF). RPUF reinforcement with varied CNC concentrations (0.25–1 wt%) was examined by foaming behavior, surface morphology, mechanical properties, thermal insulation properties, dimensional stability, efficiency energy study, and CO2 reduction through their thermal conductivity values. The results achieved an optimal improvement of mechanical properties of the RPUF composite by around 23.53% compared to RPUF control, at the addition of 0.5 wt% of CNC concentration while maintaining the density of 37–39 kg/m3. Further, incorporating CNC improved thermal insulating performance by 9.95%, as reflected by decreased thermal conductivity from 0.0292 W/mK to 0.0269 W/mK and decreased cell size by 28.12%. Finally, based on the energy and cost efficiency studies, RPUF-CNC composites offer up to 0.78 kWh/m2 and 0.031 kWh/m2 compared to conventional wall materials made of concrete and wood, respectively. Furthermore, it contributed to reduced greenhouse gas (GHG) emissions by 110 and 7.2 kg CO2/year compared to concrete and wood, respectively. This work demonstrates the promising use of eco-friendly building insulation materials to mitigate the energy and environmental crisis.

Regulating the interaction between Bi metal and Bi24O31Br10 nanosheets for efficient photoreduction of CO2

Artificial photosynthesis converting CO2 into valuable compounds has garnered significant interest. However, the insufficient surface activity sites, weak adsorption capacity of CO2 and poor electron-hole separation capability hinder CO2 photoreduction used for practical implementation. Herein, Bi nanoparticles/Bi24O31Br10 composite photocatalyst (Bi/BOB) was designed constructed through in-situ reduction of bismuth metal on the surface of ultra-thin Bi24O31Br10 nanosheets. Bi/BOB exhibits an excellent ability to reduce CO2 to CO. The CO2 reduction rate of the optimized Bi/BOB composite catalyst is 43.07 μmol·g−1·h−1, which is significantly superior to other reported bismuth-based photocatalysts. Experimental characterization and Theoretical simulation calculation reveal that the in-situ reduction of bismuth metal causes significant local lattice distortion and uneven charge distribution, thereby producing a strong interaction between Bi nanoparticles and BOB support. So, it enhances the adsorption and activation of carbon dioxide molecules and reduces the Gibbs free energy barrier during the catalytic reaction. Moreover, the strong interaction helps to enhance the separation of photogenerated charge carriers and stability of catalysts. This study offers research suggestions for the interaction between metal and support to enhance CO2 reduction.

Recent Advances in Electrochemical Carboxylation with CO2.

ConspectusCarbon dioxide (CO2) is recognized as a greenhouse gas and a common waste product. Simultaneously, it serves as an advantageous and commercially available C1 building block to generate valuable chemicals. Particularly, carboxylation with CO2 is considered a significant method for the direct and sustainable production of important carboxylic acids. However, the utilization of CO2 is challenging owing to its thermodynamic stability and kinetic inertness. Recently, organic electrosynthesis has emerged as a promising approach that utilizes electrons or holes as environmentally friendly redox reagents to produce reactive intermediates in a controlled and selective manner. This technique holds great potential for the CO2 utilization.Since 2015, our group has been dedicated to exploring the utilization of CO2 in organic synthesis with a particular focus on electrochemical carboxylation. Despite the significant advancements made in this area, there are still many challenges, including the activation of inert substrates, regulation of selectivity, diversity in electrolysis modes, and activation strategies. Over the past 7 years, our team, with many great experts, has presented findings on electrochemical carboxylation with CO2 under mild conditions. In this context, we primarily highlight our contributions to selective electrocarboxylations, encompassing new reaction systems, selectivity control methods, and activation approaches.We commenced our research by establishing a Ni-catalyzed electrochemical carboxylation of unactivated aryl halides and alkyl bromides in conjunction with a useful paired anodic reaction. This approach eliminates the need for sacrificial anodes, rendering the carboxylation process sustainable. To further utilize the widely existing yet cost-effective alkyl chlorides, we have developed a deep electroreductive system to achieve carboxylation of unactivated alkyl chlorides and poly(vinyl chloride), allowing the direct modification and upgrading of waste polymers.Through precise adjustment of the electroreductive conditions, we successfully demonstrated the dicarboxylation of both strained carbocycles and acyclic polyarylethanes with CO2 via C-C bond cleavage. Furthermore, we have realized the dicarboxylative cyclization of unactivated skipped dienes to produce the valuable ring-tethered adipic acids through single-electron reduction of CO2 to the CO2 radical anion (CO2•-). In terms of the asymmetric carboxylation, Guo's and our groups have recently achieved the nickel-catalyzed enantioselective electroreductive carboxylation reaction using racemic propargylic carbonates and CO2, paving the way for the synthesis of enantioenriched propargylic carboxylic acids.In addition to the aforementioned advancements, Lin's and our groups have also developed new electrolysis modes to achieve regiodivergent C-H carboxylation of N-heteroarenes dictated by electrochemical reactors. The choice of reactors plays a crucial role in determining whether the hydrogen atom transfer (HAT) reagents are formed anodically, consequently influencing the carboxylation pathways of N-heteroarene radical anions in the distinct electrolyzed environments.

Near-infrared-responsive sea-urchin-like Ag6Si2O7/Bi19Br3S27 S-scheme heterojunction for efficient CO2 photoreduction

The construction of S-scheme heterojunctions effectively facilitates the spatial separation of photogenerated charge carriers for their involvement in photoreactions. However, the inefficient utilization of solar energy in these heterostructures is often due to unfavorable band-edge positions and suboptimal charge transport dynamics, which result in low photocatalytic efficiency when considering kinetic factors. In this study, sea urchin–like Bi19Br3S27/Ag6Si2O7 S-scheme heterojunctions are fabricated, which exhibit excellent CO2 photoreduction performance under ultraviolet, visible, and near-infrared (NIR) light illumination. Experimental data and density functional theory calculations confirm the S-scheme charge transfer mechanisms, which enable the efficient separation of photogenerated carriers for CO2 reduction. Consequently, the optimized Ag6Si2O7/Bi19Br3S27 heterostructures exhibit superior CO2 photoreduction activity under NIR light irradiation. This approach offers a strategy for designing advanced NIR-light-responsive photocatalysts for efficient CO2 photoreduction.

Encapsulating Halide Perovskite Quantum Dots in Metal–Organic Frameworks for Efficient Photocatalytic CO2 Reduction

Halide perovskite has shown great potential in photocatalysis owing to its diversity, suitable energy band alignment, rapid charge transfer, and excellent optical properties. However, poor stability, especially under humid conditions, hinders their practical application in photocatalysis. In this work, we report the encapsulation of inorganic–organic hybrid perovskite QDs into MIL-101(Cr) through an in situ growth strategy to prepare a series of MAPbBr3@MIL-101(Cr) (MA = CH3NH3+) composites. The perovskite precursors, i.e., MABr and PbBr2, were successively introduced into the pores of MOF, where the perovskite quantum dots were self-assembled in the confined environment. In photocatalytic CO2 reduction, 11%MAPbBr3@MIL-101(Cr) composite displayed the best performance among the composites with a total CO and CH4 yield of 875 μmol g−1 in 9 h, which was 8 times higher than that of the pure MAPbBr3. Such high gas production efficiency could be maintained for 78 h at least without structural and morphologic decomposition. The remarkable stability and catalytic activity of composites are mainly due to the synergistic effect and improved electron transfer between MAPbBr3 and MIL-101(Cr). Moreover, these composites revealed a novel mechanism, showing switched CH4 selectivity with the controlling of the perovskite location and contents. Those with perovskites encapsulated in the mesopores of MIL-101(Cr) were more preferential for CO production, while those with perovskites encapsulated in both meso- and micropores could produce CH4 dominantly.