Green Carbon Science: Efficient Carbon Resource Processing, Utilization, and Recycling Towards Carbon Neutrality

Coupling methanol oxidation with CO2 reduction: A feasible pathway to achieve carbon neutralization

The energy consumption of up to 90 % of the total power input in the anodic oxygen evolution reaction (OER) slows down the implementation of electrochemical CO2 reduction reaction (CO2RR) to generate valuable chemicals. Herein, we present an alternative strategy that utilizes methanol oxidation reaction (MOR) to replace OER. The iron single atom anchored on nitrogen-doped carbon support (Fe-N-C) use as the cathode catalyst (CO2RR), low-loading platinum supported on the composites of tungsten phosphide and multiwalled carbon nanotube (Pt-WP/MWCNT) use as the anode catalyst (MOR). Our results show that the Fe-N-C exhibits a Faradaic selectivity as high as 94.93 % towards CO2RR to CO, and Pt-WP/MWCNT exhibits a peak mass activity of 544.24 mA mg-1Pt, which is 5.58 times greater than that of PtC (97.50 mA mg-1Pt). The well-established MOR||CO2RR reduces the electricity consumption up to 52.4 % compared to conventional OER||CO2RR. Moreover, a CO2 emission analysis shows that this strategy not only saves energy but also achieves carbon neutrality without changing the existing power grid structure. Our findings have crucial implications for advancing CO2 utilization and lay the foundation for developing more efficient and sustainable technologies to address the rising atmospheric CO2 levels.

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.

Enhanced CO2 Reduction on a Cu-Decorated Single-Atom Catalyst via an Inverse Sandwich M-Graphene-Cu Structure

The highly active and selective electrochemical CO2 reduction reaction (CO2RR) can be exploited to produce valuable chemicals and fuels and is also crucial for achieving clean energy goals and environmental remediation. Decorated single-atom catalysts (D-SACs), which feature synergistic interactions between the active metal site (M) and an axially decorated ligand, have been extensively explored for the CO2RR. Very recently, novel double-atom catalysts (DACs) featuring inverse sandwich structures were theoretically proposed and identified as promising CO2RR electrocatalysts. However, the experimental synthesis of DACs remains a challenge. To facilitate the fabrication and to realize the potential of these novel DACs, we designed a D-SAC system, denoted as M1@gra+Cuslab. This system features a graphene layer with a vacancy-anchored SAC, all stacked on a Cu(111) surface, thereby embodying a Cu slab-supported inverse sandwich M-graphene-Cu structure. Using density functional theory calculations, we evaluated the stability, selectivity, and activity of 27 M1@gra+Cuslab systems (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, or Au) and showed five M1@gra+Cuslab (M = Co, Ni, Cu, Rh, or Pd) systems exhibit optimal characteristics for the CO2RR and can potentially outperform their SAC and DAC counterparts. This study offers a new strategy for developing highly efficient CO2RR D-SACs with an inverse sandwich structural moiety.

Conversion of atmospheric CO2 catalyzed by thiolate-based ionic liquids under mild conditions: efficient synthesis of 2-oxazolidinones

Thiolate-based ionic liquids, specifically the catalyst [TBP][2-Tp], have demonstrated their efficiency in catalyzing the reaction of CO2 with propargylic amine. This novel synthetic method can be used to synthesize various 2-oxazolidinone derivatives with high yields. The catalyst can be easily regenerated and reused without any decline in its catalytic activity. Experimental and spectroscopic investigations have confirmed that the high activity of [TBP][2-Tp] is attributed to the synergistic effect of its S and N sites in activating CO2, rather than depending solely on basicity to activate the amino group of propargylic amine. These findings highlight the significant potential of thiolate-based ionic liquids for applications in CO2 activation and conversion.

Visible-Light-Promoted Cascade Carboxylation/Arylation of Unactivated Alkenes with CO2 for the Synthesis of Carboxylated Indole-Fused Heterocycles

Described here is a visible-light-promoted cascade carboxylation/arylation of indole-tethered unactivated alkenes with CO2 to access various carboxylated indole-fused heterocycles. This reaction is initiated by the addition of a CO2 radical anion to the alkene motif toward an alkyl carbon radical, followed by its addition to the aromatic ring, and then rearomatization to afford the final products. This reaction provides a facile and sustainable protocol for the construction of carboxylated indole-fused heterocycles using CO2 as the carboxylic source.

Controllable synthesis of hollow mesoporous organosilica nanoparticles with pyridine-2,6-bis-imidazolium frameworks for CO2 conversion

A series of hard-template-derived hollow mesoporous organosilica nanoparticles (HMONs) with pyridine-2,6-bis-imidazolium frameworks have been described for the first time. As a part of the investigation, to evaluate the effects of the hard template nature, the Si/CTAB and organosilica/TEOS molar ratios, and the stepwise addition of precursors, four reaction conditions denoted as methods A-D were designed. In the presence of polystyrene latex as a hard template, the HMONs that we wished to synthesize were not yielded with a Si/CTAB molar ratio of 3 (method A), but we could synthesize the desired HMONs with a Si/CTAB molar ratio of 9 and an organosilica : TEOS ratio of 1 : 99 (method B). The ratio of organosilica to TEOS could be improved up to 2.5 : 97.5 if the precursor additions are made in a stepwise manner rather than by simultaneous additions (method C). Using sSiO2 as a hard template, a yolk-shell morphology was observed by adopting a Si/CTAB molar ratio of 3 (method D). The HMONs were modified by iodide ions and their activity was explored toward the coupling of CO2 with epoxides. Among the catalysts, I-HMON-L-C-2.5 exhibited excellent results under mild reaction conditions. Well-oriented pore sizes and short channel length facilitated easy mass transfer from one side and the integration of the interior hollow regions of the catalyst particles from the other side improved the CO2 retention time around pores where the imidazolium organocatalysts were located, which made I-HMON-L-C-2.5 an effective catalyst for title CO2 utilization. The catalyst was reused at least six times without exhibiting any changes in its activity. HMONs can also be used as solid CNC ligands for the preparation of copper catalysts for the click reaction between phenyl acetylene and benzyl azide.

Macrocyclization of carbon dioxide with 3-triflyloxybenzynes and tetrahydrofuran: straightforward access to 14-membered macrolactones

A novel [2+2+5+5] macrocyclization of carbon dioxide with 3-triflyloxybenzynes and tetrahydrofuran has been disclosed for the first time under transition metal-free conditions. The reaction provides a facile method for the synthesis of a rare type of 14-membered macrocyclic lactone, which is potentially useful but difficult to access by existing methods.

Samarium-Oxo/Hydroxy Cluster: A Solar Photocatalyst for Chemoselective Aerobic Oxidation of Thiols for Disulfide Synthesis

Oxidation contributes as a secondary driver of the prevailing carbon emission in the chemical industries. To address this issue, photocatalytic aerobic oxidation has emerged as a promising alternative. However, the challenge of achieving satisfactory chemoselectivity and effective use of solar light has hindered progress in this area. In this context, the present study introduces a novel homogeneous photocatalyst, [Sm6O(OH)8(H2O)24]I8(H2O)8 cluster (Sm-OC), via a unique auxiliary ligand-free oxidative hydrolysis. Using Sm-OC as catalyst, a solar photocatalyzed aerobic oxidation of thiols has been developed for the synthesis of valuable disulfides. Remarkably, this catalyst manifested a significant turnover number ≥2000 under tested conditions. Sm-OC-catalyzed aerobic oxidation showcased remarkable chemoselectivity. In thiol oxidations, despite the vulnerability of disulfides toward overoxidation, overoxidized byproducts or oxidation of nontarget functional groups was not detected across all 28 tested substrates. This investigation presents the first application of a lanthanide-oxo/hydroxy cluster in photocatalysis.

Structure engineering of nickel silicate/carbon composite with boosted electrochemical performances for hybrid supercapacitors

In the wake of the carbon-neutral era, the exploration of innovative materials for energy storage and conversion has garnered increasing attention. While nickel silicates have been a focal point in energy storage research, their application in supercapacitors (SCs) has been relatively underreported due to poor conductivity. A newly designed architecture, designated as rGO@NiSiO@NiO/C (abbreviated for reduced graphene oxide (rGO), nickel silicate (NiSiO), nickel oxide/carbon (NiO/C)), has been developed to enhance the electrochemical performance of NiSiO. The incorporation of inner rGO provides structural support for NiSiO, enhancing conductivity, while the outer NiO/C layer not only boosts conductivity but also safeguards NiSiO from structural degradation and electrolyte dissolution. This architecture eliminates multi-phase mixtures, facilitating rapid electron/mass transfer kinetics and accelerating electrochemical reactions, resulting in exceptional electrochemical properties. The rGO@NiSiO@NiO/C architecture achieves a specific capacitance of 324F·g-1 at 0.5 A·g-1, with a superb cycle performance of ∼ 91 % after 10,000 cycles, surpassing state-of-the-art nickel silicates. Furthermore, the hybrid supercapacitor (HSC) device incorporating the rGO@NiSiO@NiO/C electrode attains an areal capacitance of 159 mF·cm-2 at 2.5 mA·cm-2, a retention ratio of ∼ 98 % after 10,000 cycles, and an energy density of 0.68 Wh·m-2 (26.7 Wh·kg-1) at 3.4 W·m-2 (343.8 W·kg-1). This study presents a layer-by-layer approach for constructing transition metal silicates/C architectures to enhance their electrochemical performance.

Atropisomeric Carboxylic Acids Synthesis via Nickel-Catalyzed Enantioconvergent Carboxylation of Aza-Biaryl Triflates with CO2

Upgrading CO2 to value-added chiral molecules via catalytic asymmetric C-C bond formation is a highly important yet challenging task. Although great progress on the formation of centrally chiral carboxylic acids has been achieved, catalytic construction of axially chiral carboxylic acids with CO2 has never been reported to date. Herein, we report the first catalytic asymmetric synthesis of axially chiral carboxylic acids with CO2, which is enabled by nickel-catalyzed dynamic kinetic asymmetric reductive carboxylation of racemic aza-biaryl triflates. A variety of important axially chiral carboxylic acids, which are valuable but difficult to obtain via catalysis, are generated in an enantioconvergent version. This new methodology features good functional group tolerance, easy to scale-up, facile transformation and avoids cumbersome steps, handling organometallic reagents and using stoichiometric chiral materials. Mechanistic investigations indicate a dynamic kinetic asymmetric transformation process induced by chiral nickel catalysis.

Visible Light Photoredox-Catalyzed Formyl/Carboxylation of Activated Alkenes with Glyoxylic Acid Acetals and CO2

A photoredox-catalyzed sequential α-formyl/carboxylation of alkenes with glyoxylic acid acetals and CO2 has been developed to afford a range of masked γ-formyl esters in good yields, which could be readily transformed into diverse compounds, such as γ-formyl ester, hemiacetal, and 1,4-diol. This reaction features mild conditions, readily available starting materials, and operational simplicity.

Atomically Dispersed Metal Catalysts for the Conversion of CO2 into High-Value C2+ Chemicals

The conversion of carbon dioxide (CO2) into value-added chemicals with two or more carbons (C2+) is a promising strategy that cannot only mitigate anthropogenic CO2 emissions but also reduce the excessive dependence on fossil feedstocks. In recent years, atomically dispersed metal catalysts (ADCs), including single-atom catalysts (SACs), dual-atom catalysts (DACs), and single-cluster catalysts (SCCs), emerged as attractive candidates for CO2 fixation reactions due to their unique properties, such as the maximum utilization of active sites, tunable electronic structure, the efficient elucidation of catalytic mechanism, etc. This review provides an overview of significant progress in the synthesis and characterization of ADCs utilized in photocatalytic, electrocatalytic, and thermocatalytic conversion of CO2 toward high-value C2+ compounds. To provide insights for designing efficient ADCs toward the C2+ chemical synthesis originating from CO2, the key factors that influence the catalytic activity and selectivity are highlighted. Finally, the relevant challenges and opportunities are discussed to inspire new ideas for the generation of CO2-based C2+ products over ADCs.

Atomically Dispersed p-Block Aluminum-Based Catalysts for Oxygen Reduction Reaction

The main group metals are commonly perceived as catalytically inert in the context of oxygen reduction reactions (ORR) due to the delocalized valence orbitals. Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M-Nx) is a promising approach to accelerate catalytic dynamics. Herein, we, for the first time, report the atomically dispersed Al catalysts coordinated with N and C atoms for 4-electron ORR. The axial coordinated pyrrolyl N group (No) is constructed in the Al-N4-No moiety to regulate the p-band structure of Al center, effectively steering the local environment and structure of the square planar Al-N4 sites, which typically exhibit too strong interaction with ORR intermediates. The dynamic covalency competition of axial Al-No and Al-O bonding could endow the Al center with moderate hybridization between Al 3p orbital and O 2p orbital, alleviating the binding energy of ORR intermediates. The as-prepared Al-N4-No electrocatalyst exhibits excellent ORR activity, selectivity, and durability, along with the rapid kinetics as demonstrated by in situ Raman spectroscopy. This work offers a fundamental comprehension of the fine regulation on p-band and guides the rational design of main-group metal-based single atom catalysts.

Steering CO2 Electroreduction to C2+ Products via Enhancing Localized *CO Coverage and Local Pressure in Conical Cavity

The electrochemical carbon dioxide (CO2) reduction reaction (CO2RR) involves a multistep proton-coupled electron transfer (PCET) process that generates a variety of intermediates, making it challenging to transform them into target products with high activity and selectivity. Here, a catalyst featuring a nanosheet-stacked sphere structure with numerous open and deep conical cavities (OD-CCs) is reported. Under the guidance of the finite-element method (FEM) simulations and theoretical analysis, it is shown that exerting control over the confinement space results in diffusion limitation of the carbon intermediates, thereby increasing local pressure and subsequently enhancing localized *CO coverage for dimerization. The nanocavities exhibit a structure-driven shift in selectivity of multicarbon (C2+) product from 41.8% to 81.7% during the CO2RR process.

Selective Adsorbent Design with Multifunctional Surfaces: Innovating Solutions for Heterogeneous Catalysis in Water

Heterogeneous catalytic systems with water as the solvent often have the disadvantage of cross-contamination, while concerns about the purification and workup of the aqueous phase after reactions are rare in the lab or industry. In this context, designing and developing the functional selective solid adsorbent and revealing the adsorption mechanism can provide a new strategy and guidelines for constructing supported heterogeneous catalysts to address these issues. Herein, we report the stable composite adsorbent (Fe/ATP@PPy: magnetic Fe3O4/attapulgite with the polypyrrole shell) that features an integrated multifunctional surface, which can effectively tune the selective adsorption processes for Cu2+, Co2+, and Ni2+ ions and nitrobenzene via the cooperative chemisorption/physisorption in an aqueous system. The adsorption experiments showed that Fe/ATP@PPy displayed significantly higher adsorption selectivity for Ni2+ than Cu2+ and Co2+ ions, especially which exhibited an approximate 100.00% removal for both Ni2+ ions and nitrobenzene in the mixture system with a low concentration. Furthermore, combined tracking adsorption of Ni2+ ions and X-ray photoelectron spectroscopy characterization confirmed that the effective adsorption occurs via ion transfer coordination; the pathway was further validated at the molecular level through theoretical modeling. In addition, the selective adsorption mechanism was proposed based on the adsorption experiment, characterization, and the corresponding density functional theory calculation.

Nitrogenous Intermediates in NOx-involved Electrocatalytic Reactions

Chemical manufacturing utilizing renewable sources and energy emerges as a promising path towards sustainability and carbon neutrality. The electrocatalytic reactions involving nitrogen oxides (NOx) offered a potential strategy for synthesizing various nitrogenous chemicals. However, it is currently hindered by low selectivity/efficiency and limited reaction pathways, mainly due to the difficulties in controllable generation and utilization of nitrogenous intermediates. In this minireview, focusing on nitrogenous intermediates in NOx-involved electrocatalytic reactions, we discuss newly developed methodologies for studying and controlling the generation, conversion, and utilizing of nitrogenous intermediates, which enable recent developments in NOx-involved electrocatalytic reactions that yield various products, including ammonia (NH3), organonitrogen molecules, and nitrogenous compounds exhibiting unconventional oxidation states. Furthermore, we also make an outlook to highlight future directions in the emerging field of NOx-involved electrocatalytic reactions.

Dissolution and regeneration of starch in hydroxyl-functionalized ionic liquid aqueous solution

There have been continuous quests for suitable solvents for starch, given the importance of effective starch dissolution in its modification and subsequent materials production. In light of this, the potential of hydroxyl-functionalized ionic liquid (IL) as a promising solvent for starch was investigated. Within this study, a hydroxyl-functionalized IL 1-(2,3-dihydroxypropyl)-3-methylimidazole chloride ([Dhpmim][Cl]) was synthesized, and the dissolution of starch in this IL and its aqueous solutions was examined. Starch (5.35 wt%) was completely dissolved in [Dhpmim][Cl] within 2 h at 100 °C. The solubility of starch in [Dhpmim][Cl]-water mixtures initially increased and then decreased with rising water content. The optimal ratio was found to be 1:9 (wt/wt) water:[Dhpmim][Cl], achieving the highest solubility at 9.28 wt%. Density functional theory (DFT) simulations elucidated the possible interactions between starch and solvents. After dissolution and regeneration in the 1:9 water:[Dhpmim][Cl] mixture, starch showed no discernible change in the molecular structure, with no derivatization reaction observed. Regenerated starch exhibited a transformation in crystalline structure from A-type to V-type, and its relative crystallinity (12.4 %) was lower than that of native starch (25.2 %), resulting in decreased thermal stability. This study suggests that the hydroxyl-functionalized IL, [Dhpmim][Cl], and its aqueous solutions serve as effective solvents for starch dissolution.

Insight into the Feasibility of Fatty Acyl Chlorides with 10-18 Carbons for the Ball-Milling Synthesis of Thermoplastic Cellulose Esters

Fatty acid cellulose esters (FACE) are common cellulose-based thermoplastics, and their thermoplasticity is determined by both the contents and the lengths of the side chains. Herein, various FACE were synthesized by the ball-milling esterification of cellulose and fatty acyl chlorides containing 10-18 carbons, and their structures and thermoplasticity were thoroughly studied. The results showed that FACE with high degrees of substitution (DS) and low melting flow temperatures (Tf) were achieved as the chain lengths of the fatty acyl chlorides were reduced. In particular, a cellulose decanoate with a DS of 1.85 and a Tf of 186 °C was achieved by feeding 3 mol of decanoyl chloride per mole anhydroglucose units of cellulose. However, cellulose stearate (DS = 1.53) synthesized by the same protocols cannot melt even at 250 °C. More interestingly, the fatty acyl chlorides with 10 and 12 carbons resulted in FACE with superior toughness (elongation at break up to 94.4%). In contrast, due to their potential crystallization of the fatty acyl groups with 14-18 carbons, the corresponding FACE showed higher tensile strength and Young's modulus than the others. This study provides some theoretical basis for the mechanochemical synthesis of thermoplastic FACE with designated properties.

Isomorphic Insertion of Ce(III)/Ce(IV) Centers into Layered Double Hydroxide as a Heterogeneous Multifunctional Catalyst for Efficient Meerwein-Ponndorf-Verley Reduction

The development of highly active acid-base catalysts for transfer hydrogenations of biomass derived carbonyl compounds is a pressing challenge. Solid frustrated Lewis pairs (FLP) catalysis is possibly a solution, but the development of this concept is still at a very early stage. Herein, stable, phase-pure, crystalline hydrotalcite-like compounds were synthesized by incorporating cerium cations into layered double hydroxide (MgAlCe-LDH). Besides the insertion of well-isolated cerium centers surrounded by hydroxyl groups, the formation of hydroxyl vacancies near the aluminum centers, which were formed by the insertion of cerium centers into the layered double hydroxides (LDH) lattice, was also identified. Depending on the initial cerium concentration, LDHs with different Ce(III)/Ce(IV) ratios were produced, which had Lewis acidic and basic characters, respectively. However, the acid-base character of these LDHs was related to the actual Ce(III)/Ce(IV) molar ratios, resulting in significant differences in their catalytic performance. The as-prepared structures enabled varying degrees of transfer hydrogenation (Meerwein-Ponndorf-Verley MPV reduction) of biomass-derived carbonyl compounds to the corresponding alcohols without the collapse of the original lamellar structure of the LDH. The catalytic markers through the test reactions were changed as a function of the amount of Ce(III) centers, indicating the active role of Ce(III)-OH units. However, the cooperative interplay between the active sites of Ce(III)-containing specimens and the hydroxyl vacancies was necessary to maximize catalytic efficiency, pointing out that Ce-containing LDH is a potentially commercial solid FLP catalysts. Furthermore, the crucial role of the surface hydroxyl groups in the MPV reactions and the negative impact of the interlamellar water molecules on the catalytic activity of MgAlCe-LDH were demonstrated. These solid FLP-like catalysts exhibited excellent catalytic performance (cyclohexanol yield of 45%; furfuryl alcohol yield of 51%), which is competitive to the benchmark Sn- and Zr-containing zeolite catalysts, under mild reaction conditions, especially at low temperature (T = 65 °C).

Production of Biobased Ethylbenzene by Cascade Biocatalysis with an Engineered Photodecarboxylase

Production of commodity chemicals, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), from renewable resources is key for a sustainable society. Biocatalysis enables one-pot multistep transformation of bioresources under mild conditions, yet it is often limited to biochemicals. Herein, we developed a non-natural three-enzyme cascade for one-pot conversion of biobased l-phenylalanine into ethylbenzene. The key rate-limiting photodecarboxylase was subjected to structure-guided semirational engineering, and a triple mutant CvFAP(Y466T/P460A/G462I) was obtained with a 6.3-fold higher productivity. With this improved photodecarboxylase, an optimized two-cell sequential process was developed to convert l-phenylalanine into ethylbenzene with 82 % conversion. The cascade reaction was integrated with fermentation to achieve the one-pot bioproduction of ethylbenzene from biobased glycerol, demonstrating the potential of cascade biocatalysis plus enzyme engineering for the production of biobased commodity chemicals.

Photo-thermal coupling to enhance CO2 hydrogenation toward CH4 over Ru/MnO/Mn3O4

Upcycling of CO2 into fuels by virtually unlimited solar energy provides an ultimate solution for addressing the substantial challenges of energy crisis and climate change. In this work, we report an efficient nanostructured Ru/MnOx catalyst composed of well-defined Ru/MnO/Mn3O4 for photo-thermal catalytic CO2 hydrogenation to CH4, which is the result of a combination of external heating and irradiation. Remarkably, under relatively mild conditions of 200 °C, a considerable CH4 production rate of 166.7 mmol g-1 h-1 was achieved with a superior selectivity of 99.5% at CO2 conversion of 66.8%. The correlative spectroscopic and theoretical investigations suggest that the yield of CH4 is enhanced by coordinating photon energy with thermal energy to reduce the activation energy of reaction and promote formation of key intermediate COOH* species over the catalyst. This work opens up a new strategy for CO2 hydrogenation toward CH4.

Recent progress of heterogeneous catalysts for transfer hydrogenation under the background of carbon neutrality

Under the background of carbon neutrality, the direct conversion of greenhouse CO2 to high value added fuels and chemicals is becoming an important and promising technology. Among them, the generation of liquid C1 products (formic acid and methanol) has made great progress; nevertheless, it encounters the problem of how to use it efficiently to solve the overcapacity issue. In this review, we suggest that the catalytic transfer hydrogenation using formic acid and methanol as the hydrogen sources is a critical and potential route for the substitution for the fossil fuel-derived H2 to generate essential bulk and fine chemicals. We mainly focus on summarizing the recent progress of heterogeneous catalysts in such reactions, including thermal- and photo-catalytic processes. Finally, we also propose some challenges and opportunities for this development.

Adjusted Preferential Adsorption of Intermediates via Regulation of the Electronic Structure during the Electrocatalytic CO2 Reduction Process

The surface electronic structures of catalysts play a crucial role in CO2 adsorption and activation. Here, sulfur vacancies are introduced into CuInS2 nanosheets (Vs-CuInS2) to evaluate the effect of electronic structures at the surface-active sites on the electrochemical CO2 reduction reaction (CO2RR). Vs-CuInS2 exhibits a significant disparity in the highest FEformate/FECO (6.50) compared to that of CuInS2 (1.86). Specifically, the maximum current density (Jmax) of carbon products on Vs-CuInS2 is 78.78 mA cm-2, and a Faraday efficiency of carbon products (FEcarbon products) of ≥80% is achieved in 600 mV wide potential windows. In situ Raman measurements and density functional theory calculations elucidate the origin of the apparent alterations in the carbon product selectivity. The introduction of sulfur vacancies realizes the controllable regulation of the local electronic density around the metal active sites, inducing the transformation of *COOH and *OCHO from competitive adsorption on CuInS2 to specific adsorption on Vs-CuInS2. In addition, the regulation of electronic structures on Vs-CuInS2 inhibits *H adsorption. This work reveals the transfer of adsorption of CO2RR intermediates via regulation of the electronic structure, complementing the understanding of the mechanism for the enhanced CO2RR.

Elucidating protonation pathways in CO2 photoreduction using the kinetic isotope effect

The surge in anthropogenic CO2 emissions from fossil fuel dependence demands innovative solutions, such as artificial photosynthesis, to convert CO2 into value-added products. Unraveling the CO2 photoreduction mechanism at the molecular level is vital for developing high-performance photocatalysts. Here we show kinetic isotope effect evidence for the contested protonation pathway for CO2 photoreduction on TiO2 nanoparticles, which challenges the long-held assumption of electron-initiated activation. Employing isotopically labeled H2O/D2O and in-situ diffuse reflectance infrared Fourier transform spectroscopy, we observe H+/D+-protonated intermediates on TiO2 nanoparticles and capture their inverse decay kinetic isotope effect. Our findings significantly broaden our understanding of the CO2 uptake mechanism in semiconductor photocatalysts.

Visible-Light Photoredox-Catalyzed Intermolecular α-Aminomethyl/Carboxylative Dearomatization of Indoles with CO2 and α-Aminoalkyl Radical Precursors

Disclosed here is a visible-light photoredox-catalyzed intermolecular sequential α-aminomethyl/carboxylative dearomatization of indoles with CO2 and α-aminoalkyl radical precursors, affording a series of functionalized indoline-3-carboxylic acids and lactams in good yields with high regioselectivity. This multicomponent reaction provides a green and facile method for the synthesis of diverse functionalized indolines by using CO2 as the carboxylic and carbonyl source.

Palladium(II)-immobilized Triptycene based Hypercrosslinked Polymers: An Efficient, Green, and Reusable Heterogenous Catalyst for Suzuki-Miyaura Cross-coupling Reaction

The Suzuki-Miyaura cross-coupling (SMCC) involves the coupling of organohalides and organoboron molecules in the presence of Pd(II)-based catalysts. Often SMCC reactions employ homogenous catalysts. However, such homogenous SMCC reactions are associated with certain limitations which has motivated design of effective and sustainable Pd(II)-based heterogeneous catalytic systems. Herein, we report a systematic development of a Pd(II)-immobilized and triptycene based ionic hyper crosslinked polymer (Pd@TP-iHCP) and explored its application as a heterogeneous catalyst for SMCC reaction. Pd@TP-iHCP has ample N-heterocyclic carbene (NHC) pendants that anchor Pd(II) centres on the polymeric matrix. Pd@TP-iHCP was characterized satisfactorily using FT-IR, 13 C CP-MAS NMR, BET surface area analysis, SEM, EDX and HRTEM. The performance of Pd@TP-iHCP as a heterogeneous catalyst for SMCC reactions was explored using various combinations of aryl boronic acids and aryl halides. Experimental results show that Pd@TP-iHCP is associated with a moderately high surface area. It is an efficient catalyst for SMCC (in aqueous media) with a modest loading of 0.8 mol % Pd(II)-catalyst since high yields of the expected products were obtained in shorter time intervals. Pd@TP-iHCP also features excellent stability and catalyst recyclability since it could be re-used for several cycles without any significant decrease in catalytic efficiency.

Enhancing photoelectrochemical CO2 reduction with silicon photonic crystals

The effectiveness of silicon (Si) and silicon-based materials in catalyzing photoelectrochemistry (PEC) CO2 reduction is limited by poor visible light absorption. In this study, we prepared two-dimensional (2D) silicon-based photonic crystals (SiPCs) with circular dielectric pillars arranged in a square array to amplify the absorption of light within the wavelength of approximately 450 nm. By investigating five sets of n + p SiPCs with varying dielectric pillar sizes and periodicity while maintaining consistent filling ratios, our findings showed improved photocurrent densities and a notable shift in product selectivity towards CH4 (around 25% Faradaic Efficiency). Additionally, we integrated platinum nanoparticles, which further enhanced the photocurrent without impacting the enhanced light absorption effect of SiPCs. These results not only validate the crucial role of SiPCs in enhancing light absorption and improving PEC performance but also suggest a promising approach towards efficient and selective PEC CO2 reduction.

Directly Knitted Hierarchical Porous Organometallic Polymer-Based Self-Supported Single-Site Catalyst for CO2 Hydrogenation in Water

In recent times, heterogenization of homogeneous molecular catalysts onto various porous solid support structures has attracted significant research focus as a method for combining the advantages of both homogeneous as well as heterogeneous catalysis. The design of highly efficient, structurally robust and reusable heterogenized single-site catalysts for the CO2 hydrogenation reaction is a critical challenge that needs to be accomplished to implement a sustainable and practical CO2 -looped renewable energy cycle. This study demonstrated a heterogenized catalyst [Ir-HCP-(B/TPM)] containing a molecular Ir-abnormal N-heterocyclic carbene (Ir-aNHC) catalyst self-supported by hierarchical porous hyper-crosslinked polymer (HCP), in catalytic hydrogenation of CO2 to inorganic formate (HCO2 - ) salt that is a prospective candidate for direct formate fuel cells (DFFC). By employing this unique and first approach of utilizing a directly knitted HCP-based organometallic single-site catalyst for CO2 -to-HCO2 - in aqueous medium, extremely high activity with a single-run turnover number (TON) up to 50816 was achieved which is the highest so far considering all the heterogeneous catalysts for this reaction in water. Additionally, the catalyst featured excellent reusability furnishing a cumulative TON of 285400 in 10 cycles with just 1.6 % loss in activity per cycle. Overall, the new catalyst displayed attributes that are important for developing tangible catalysts for practical applications.

Integration of plasma and electrocatalysis to synthesize cyclohexanone oxime under ambient conditions using air as a nitrogen source

Direct fixation of N2 to N-containing value-added chemicals is a promising pathway for sustainable chemical manufacturing. There is extensive demand for cyclohexanone oxime because it is the essential feedstock of Nylon 6. Currently, cyclohexanone oxime is synthesized under harsh conditions that consume a considerable amount of energy. Herein, we report a novel approach to synthesize cyclohexanone oxime by in situ NO3- generation from air under ambient conditions. This process was carried out through an integrated strategy including plasma-assisted air-to-NOx and co-electrolysis of NOx and cyclohexanone. A high rate of cyclohexanone oxime formation at 20.1 mg h-1 cm-2 and a corresponding faradaic efficiency (FE) of 51.4% was achieved over a Cu/TiO2 catalyst, and the selectivity of cyclohexanone oxime was >99.9% on the basis of cyclohexanone. The C-N bond formation mechanism was examined by in situ experiments and theoretical calculations, which showed that cyclohexanone oxime forms through the reaction between an NH2OH intermediate and cyclohexanone.

Accelerating multielectron reduction at CuxO nanograins interfaces with controlled local electric field

Regulating electron transport rate and ion concentrations in the local microenvironment of active site can overcome the slow kinetics and unfavorable thermodynamics of CO2 electroreduction. However, simultaneous optimization of both kinetics and thermodynamics is hindered by synthetic constraints and poor mechanistic understanding. Here we leverage laser-assisted manufacturing for synthesizing CuxO bipyramids with controlled tip angles and abundant nanograins, and elucidate the mechanism of the relationship between electron transport/ion concentrations and electrocatalytic performance. Potassium/OH- adsorption tests and finite element simulations corroborate the contributions from strong electric field at the sharp tip. In situ Fourier transform infrared spectrometry and differential electrochemical mass spectrometry unveil the dynamic evolution of critical *CO/*OCCOH intermediates and product profiles, complemented with theoretical calculations that elucidate the thermodynamic contributions from improved coupling at the Cu+/Cu2+ interfaces. Through modulating the electron transport and ion concentrations, we achieve high Faradaic efficiency of 81% at ~900 mA cm-2 for C2+ products via CO2RR. Similar enhancement is also observed for nitrate reduction reaction (NITRR), achieving 81.83 mg h-1 ammonia yield rate per milligram catalyst. Coupling the CO2RR and NITRR systems demonstrates the potential for valorizing flue gases and nitrate wastes, which suggests a practical approach for carbon-nitrogen cycling.

Single-walled carbon nanotubes synthesized by laser ablation from coal for field-effect transistors

Single-walled carbon nanotubes (SWCNTs) have been attracting extensive attention due to their excellent properties. We have developed a strategy of using coal to synthesize SWCNTs for high performance field-effect transistors (FETs). The high-quality SWCNTs were synthesized by laser ablation using only coal as the carbon source and Co-Ni as the catalyst. We show that coal is a carbon source superior to graphite with higher yield and better selectivity toward SWCNTs with smaller diameters. Without any pre-purification, the as-prepared SWCNTs were directly sorted based on their conductivity and diameter using either aqueous two-phase extraction or organic phase extraction with PCz (poly[9-(1-octylonoyl)-9H-carbazole-2,7-diyl]). The semiconducting SWCNTs sorted by one-step PCz extraction were used to fabricate thin film FETs. The transformation of coal into FETs (and further integrated circuits) demonstrates an efficient way of utilizing natural resources and a marvelous example in green carbon technology. Considering its short steps and high feasibility, it presents great potential in future practical applications not limited to electronics.

Highly efficient zinc electrode prepared by electro-deposition in a salt-induced pre-phase separation region solution

Efficient electrode design is crucial for the electrochemical reduction of CO2 to produce valuable chemicals. The solution used for the preparation of electrodes can affect their overall properties, which in turn determine the reaction efficiency. In this work, we report that transition metal salts could induce the change of two-phase ionic liquid/ethanol mixture into miscible one phase. Pre-phase separation region near the phase boundary of the ternary system was observed. Zinc nanoparticles were electro-deposited along the fibres of carbon paper (CP) substrate uniformly in the salt-induced pre-phase separation region solution. The as-prepared Zn(1)/CP electrode exhibits super-wettability to the electrolyte, rendering very high catalytic performance for CO2 electro-reduction, and the Faradaic efficiency towards CO is 97.6% with a current density of 340 mA cm-2, which is the best result to date in an H-type cell.

Distinct Selectivity Control in Solar-Driven Bio-Based α-Hydroxyl Acid Conversion: A Comparison of Pt Nanoparticles and Atomically Dispersed Pt on CdS

Solar-driven photocatalytic lignocellulose conversion is a promising strategy for the sustainable production of high-value chemicals, but selectivity control remains a challenging goal in this field. Here, we report efficient and selective conversion of lignocellulose-derived α-hydroxyl acids to tartaric acid derivatives, α-keto acids, and H2 using Pt-modified CdS catalysts. Pt nanoparticles on CdS selectively produce tartaric acid derivatives via C-C coupling, while atomically dispersed Pt on CdS switches product selectivity to the oxidation reaction to produce α-keto acids. The atomically dispersed Pt species stabilized by Pt-S bonds promote the activation of the hydroxyl group and thus switch product selectivity from tartaric acid derivatives to α-keto acids. A broad range of lignocellulose-derived α-hydroxyl acids was applied for preparing the corresponding tartaric acid derivatives and α-keto acids over the two Pt-modified CdS catalysts. This work highlights the unique performance of metal sulfides in coupling reactions and demonstrates a strategy for rationally tuning product selectivity by engineering the interaction between metal sulfide and cocatalyst.

Modulating the Reaction Configuration by Breaking the Structural Symmetry of Active Sites for Efficient Photocatalytic Reduction of Low-concentration CO2

Photocatalytic conversion of low-concentration CO2 is considered as a promising way to simultaneously mitigate the environmental and energy issues. However, the weak CO2 adsorption and tough CO2 activation process seriously compromise the CO production, due to the chemical inertness of CO2 molecule and the formed fragile metal-C/O bond. Herein, we designed and fabricated oxygen vacancy contained Co3 O4 hollow nanoparticles on ordered macroporous N-doped carbon framework (Vo-HCo3 O4 /OMNC) towards photoreduction of low-concentration CO2 . In situ spectra and ab initio molecular dynamics simulations reveal that the constructed oxygen vacancy is able to break the local structural symmetry of Co-O-Co sites. The formation of asymmetric active site switches the CO2 configuration from a single-site linear model to a multiple-sites bending one with a highly stable configuration, enhancing the binding and structural polarization of CO2 molecules. As a result, Vo-HCo3 O4 /OMNC shows unprecedent activity in the photocatalytic conversion of low-concentration CO2 (10 % CO2 /Ar) under laboratory light source or even natural sunlight, affording a syngas yield of 337.8 or 95.2 mmol g-1  h-1 , respectively, with an apparent quantum yield up to 4.2 %.

P-Band Intermediate States Mediate Electron Transfer at Confined Nanoscale

In this Perspective, mainly based on the model of structural water molecules (SWs) as bright color emitters, we briefly summarize the development and theoretical elaboration of P-band intermediate state (PBIS) theory as well as its application in several typical catalytic redox reactions. In addition, with a simple equation (2∫ψ2σ1' + ∫ψ2σ2 + ∫ψ2π = 1), we clearly define how the interface states correlate with the three basic parameters of heterogeneous catalysis (conversion, selectivity, and stability), and what is the dynamic nature of catalytic active sites. Overall, the proposal of SW-dominated PBIS theory establishes an internal physical connection between the decay kinetics of excited electrons and the catalytic reaction kinetics and provides new insights into the physical origin of photoluminescence emission of low-dimensional quantum nanodots and the physical nature of nanoconfinement and nanoconfined catalysis.

Platinum Species on Oxygen Vacancy-Rich Titania for Efficient Basic Electrocatalytic Hydrogen Evolution

Oxygen vacancy-rich titania is a promising support for enhancing the hydrogen evolution reaction (HER). This work innovatively loaded Pt nanoparticles on oxygen vacancy-rich TiO2 (Pt/Vo-TiO2) in situ by using a photocatalytic device. The synthesis conditions are mild, do not require high temperatures and strong reducing agents, and can avoid the accumulation of platinum species. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectrometry (XAS) verified the synergistic effect of Pt species and oxygen vacancies on the progress of the reaction kinetics, where the Pt particles exposed by the in situ synthesis functioned as reaction sites in the electrocatalytic hydrogen evolution. Based on this, Pt/Vo-TiO2 exhibits excellent electrocatalytic performance with an overpotential of only 56 mV at a current density of 10 mA cm-2 and a Tafel slope of only 73.5 mV dec-1. This work provides a new strategy for designing highly efficient HER catalysts.

Green carbon science: fundamental aspects

Carbon energy has contributed to the creation of human civilization, and it can be considered that the configuration of the carbon energy system is one of the important laws that govern the operation of everything in the universe. The core of the carbon energy system is the opposition and unity of two aspects: oxidation and reduction. The operation of oxidation and reduction is based on the ternary elemental system composed of the three elements of carbon, hydrogen and oxygen. Its operation produces numerous reactions and reaction products. Ancient Chinese philosophy helps us to understand in depth the essence of green carbon science, to explore its scientific basis, and to identify the related platforms for technology development.

Amine-Assisted Simultaneous CO2 Absorption and Mineral Carbonation: Effect of Different Categories of Amines

The hybrid technology of CO₂ capture-mineral carbonation (CCMC) using alkaline streams has emerged in recent years. However, thus far, there has been no comprehensive study revealing the mechanisms of the simultaneous CCMC process regarding the choice of amine types and sensitivity of parameters. Combining with the analysis of multistep reaction mechanisms for different amines, we investigated a representative from each category in CCMC using calcium chloride to simulate the alkaline resource after leaching, i.e., primary (ethanolamine, MEA), secondary (diisopropanolamine, DIPA), tertiary (diethylethanolamine, DEAE), and triamine (diethylenetriamine, DETA), respectively. In the adsorption step, increasing the amine concentration beyond 2 mol/L reduced the absorption efficiency of DEAE due to the hydration mechanism, motivating a rational choice of concentration. In CCMC sections, when the amine concentration increased, only DEAE exhibited an increased carbonation efficiency of up to 100%, while DETA showed the lowest conversion. The carbonation of DEAE demonstrated the least sensitivity to temperature. The crystal transformation experiments suggested that over time, the produced vaterite could completely transform to calcite or aragonite, except those from DETA. Thus, with rationally chosen conditions, DEAE was demonstrated ideal for CCMC. These findings obtained in this work provided a theoretical foundation for designing future CCMC processes.

One-Pot Synthesis of Dihydropyrans via CO2 Reduction and Domino Knoevenagel/oxa-Diels-Alder Reactions

Catalytic CO₂ reduction with phenylsilane under solvent-free conditions was linked with the one-pot synthesis of 3,4-dihydropyrans from β-dicarbonyl compounds and styrenes. The synthesis includes three processes: (1) bis(silyl)acetal formation from CO₂ and phenylsilane and a domino reaction of (2) Knoevenagel condensation and (3) inverse-electron-demand oxa-Diels-Alder reaction. The first process was catalyzed by a pentanuclear Zn^II complex (0.07 mol %) to generate bis(silyl)acetals, which were hydrolyzed into formaldehyde to be used in the second step.

Photocatalytic Carboxylation of C-N Bonds in Cyclic Amines with CO2 by Consecutive Visible-Light-Induced Electron Transfer

Visible-light photocatalytic carboxylation with CO₂ is highly important. However, it still remains challenging for reluctant substrates with low reduction potentials. Herein, we report a novel photocatalytic carboxylation of C-N bonds in cyclic amines with CO₂ via consecutive photo-induced electron transfer (ConPET). It is also the first photocatalytic reductive ring-opening reaction of azetidines, pyrrolidines and piperidines. This strategy is practical to transform a variety of easily available cyclic amines to valuable β-, γ-, δ- and ϵ-amino acids in moderate-to-excellent yields. Moreover, the method also features mild and transition-metal-free conditions, high selectivity, good functional-group tolerance, facile scalability and product derivations. Mechanistic studies indicate that the ConPET might be the key to generating highly reactive photocatalysts, which enable the reductive activation of cyclic amines to generate carbon radicals and carbanions as the key intermediates.

Tailoring inkjet-printed PEDOT:PSS composition toward green, wearable device fabrication

Inkjet printing remains one of the most cost-efficient techniques for device prototyping and manufacturing, offering considerable freedom of digital design, non-contact, and additive fabrication. When developing novel wearable devices, a balanced approach is required between functional, user-safe materials and scalable manufacturing processes. Here, we propose a tailor-made ink formulation, based on non-hazardous materials, to develop green electronic devices aimed at interfacing with humans. We demonstrate that developed ink exhibits high-resolution inkjet printability, in line with theoretical prediction, on multiple wearable substrates. The ink's chemical composition ensures the pattern's enhanced electrical properties, mechanical flexibility, and stability in water. The cytocompatibility evaluations show no noxious effects from printed films in contact with human mesenchymal stem cells. Finally, we fabricated a printed wearable touch sensor on a non-woven fabric substrate, capable of tracking human steps. This is a step toward the development of green wearable electronics manufacturing, demonstrating a viable combination of materials and processes for biocompatible devices.

Transition Metal Phosphide Nanoarchitectonics for Versatile Organic Catalysis

Transition metal phosphides (TMP) posses unique physiochemical, geometrical, and electronic properties, which can be exploited for different catalytic applications, such as photocatalysis, electrocatalysis, organic catalysis, etc. Among others, the use of TMP for organic catalysis is less explored and still facing many complex challenges, which necessitate the development of sustainable catalytic reaction protocols demonstrating high selectivity and yield of the desired molecules of high significance. In this regard, the controlled synthesis of TMP-based catalysts and thorough investigations of underlying reaction mechanisms can provide deeper insights toward practical achievement of desired applications. This review aims at providing a comprehensive analysis on the recent advancements in the synthetic strategies for the tailored and tunable engineering of structural, geometrical, and electronic properties of TMP. In addition, their unprecedented catalytic potential toward different organic transformation reactions is succinctly summarized and critically analyzed. Finally, a rational perspective on future opportunities and challenges in the emerging field of organic catalysis is provided. On the account of the recent achievements accomplished in organic synthesis using TMP, it is highly anticipated that the use of TMP combined with advanced innovative technologies and methodologies can pave the way toward large scale realization of organic catalysis.

Continuously Flow Photothermal Catalysis Efficiently CO2 Reduction Over S-Scheme 2D/0D Bi5 O7 I-OVs/Cd0.5 Zn0.5 S Heterojunction with Strong Interfacial Electric Field

Using CO₂ , water, and sunlight to produce solar fuel is a very attractive process, which can synchronously reduce carbon and convert solar energy into hydrocarbons. However, photocatalytic CO₂ reduction is often limited by the low selectivity of reduction products and poor photocatalytic activity. In this study, S-scheme Bi₅ O₇ I-OVs/Cd_0.5 Zn_0.5 S (Bi₅ O₇ I-OVs/CZS-0.5) heterojunction with strong interfacial electric field (IEF) is prepared by in situ growth method. The performance of reduction CO₂ to CO is studied by continuous flow photothermal catalytic (PTC) CO₂ reduction platform. 12.5% Bi₅ O₇ I-OVs/CZS-0.5 shows excellent CO yield of 58.6 µmol g^-1  h^-1 and selectivity of 98.4%, which are 35.1 times than that of CZS-0.5 under visible light. The charge transfer path of the S-scheme through theoretical calculation (DFT), in situ irradiation Kelvin probe force microscope (ISI-KPFM) and in situ irradiation X-ray photoelectron spectroscopy (ISI-XPS) analysis, is verified. The study can provide useful guidance and reference for improving activity by oxygen vacancy induced strong IEF and the development of a continuous flow PTC CO₂ reduction system.

Guanidine-Based Covalent Organic Frameworks: Cooperation between Cores and Linkers for Chromic Sensing and Efficient CO2 Conversion

C(sp)-H carboxylation with CO₂ is an attractive route of CO₂ utilization and is traditionally promoted by transition metal catalysts, and organocatalysis for the conversion remains rarely explored and challenging. In this article, triaminoguanidine-derived covalent organic frameworks (COFs) were used as platforms to develop heterogeneous organocatalysts for the reaction. We demonstrated that the COFs with guanidine cores and pyrazine linkers show high catalytic performance as a result of the cooperation between cores and linkers. The core is vitally important, which is deprotonated to the guanidinato group that binds and activates CO₂. The pyrazine linker collaborates with the core to activate the C(sp)-H bond through hydrogen bonding. In addition, the COFs show acid- and base-responsive chromic behaviors thanks to the amphoteric nature of the core and the auxochromic effect of the pyrazine linker. The work opens up new avenues to organocatalysts for C-H carboxylation and chromic materials for sensing and switching applications.

Advancements and Challenges in Reductive Conversion of Carbon Dioxide via Thermo-/Photocatalysis

Carbon dioxide (CO₂) is the major greenhouse gas and also an abundant and renewable carbon resource. Therefore, its chemical conversion and utilization are of great attraction for sustainable development. Especially, reductive conversion of CO₂ with energy input has become a current hotspot due to its ability to access fuels and various important chemicals. Nowadays, the controllable CO₂ hydrogenation to formic acid and alcohols using sustainable H₂ resources has been regarded as an appealing solution to hydrogen storage and CO₂ accumulation. In addition, photocatalytic CO₂ reduction to CO also provides a potential way to utilize this greenhouse gas efficiently. Besides direct CO₂ hydrogenation, CO₂ reductive functionalization integrates CO₂ reduction with subsequent C-X (X = N, S, C, O) bond formation and indirect transformation strategies, enlarging the diverse products derived from CO₂ and promoting CO₂ reductive conversion into a new stage. In this Perspective, the progress and challenges of CO₂ reductive conversion, including hydrogenation, reductive functionalization, photocatalytic reduction, and photocatalytic reductive functionalization are summarized and discussed along with the key issues and future trends/directions in this field. We hope this Perspective can evoke intense interest and inspire much innovation in the promise of CO₂ valorization.

A Bio-Based Supramolecular Adhesive: Ultra-High Adhesion Strengths at both Ambient and Cryogenic Temperatures and Excellent Multi-Reusability

Developing high-performance and reusable adhesives from renewable feedstocks is of significance to sustainable development, yet it still remains a formidable task. Herein, castor oil, melevodopa, and iron ions are used as building blocks to construct a novel bio-based supramolecular adhesive (BSA) with outstanding adhesion performances. It is prepared through partial coordination between melevodopa functionalized castor oil and Fe3+ ions. Noncovalent interactions between adherends and the catechol unit from melevodopa contribute to reinforcing adhesion, and the metal-ligand coordination between catechol and Fe3+ ions is utilized to strengthen cohesion. By combining strong adhesion and tough cohesion, the prepared BSA achieves an adhesion strength of 14.6 MPa at ambient temperature, a record-high value among reported bio-based adhesives as well as supramolecular adhesives to the best of knowledge. It also outperforms those adhesives at cryogenic temperature, realizing another record-high adhesion strength of 9.5 MPa at -196 °C. In addition, the BSA displays excellent multi-reusability with more than 87% of the original adhesion strength remaining even after reuse for ten times. It is highly anticipated that this line of research will provide a new insight into designing bio-based adhesives with outstanding adhesion performances and excellent multi-reusability.

Construction of SrTiO3–LaCrO3 Solid Solutions with Consecutive Band Structures for Photocatalytic H2 Evolution under Visible Light Irradiation

SrTiO3–LaCrO3 continuous solid solutions with LaCrO3 content ranging from 0.00 to 1.00 were prepared via a polymerized complex method. The light absorption ability of SrTiO3 was improved by the consecutive tuning of the bandgap upon the introduction of LaCrO3 (up to 570 nm). The solid solutions exhibited significantly enhanced photocatalytic activities for H2 evolution under visible light irradiation, with an optimized H2 evolution rate of 1368 μmol h−1 g−1 obtained when LaCrO3 content was 0.10 (with 1 wt% Pt as cocatalyst), corresponding to an apparent quantum yield of 3.68% at 400 nm. Supported by comprehensive characterization, the improved photocatalytic performance was attributed to the simultaneously adjusted conduction band and valance band originating from the hybridization of Cr 3d, Ti 3d and O 2p orbitals, as well as the accelerated separation and migration of photogenerated charge carriers derived from the distortion of TiO6 octahedra.