Supramolecular Complexation-enhanced CO2 Chemisorption in Amine-derived Sorbents.

A supramolecular complexation approach is developed to improve the CO2 chemisorption performance of solvent-lean amine sorbents. Operando spectroscopy techniques reveal the formation of carbamic acid in the presence of a crown ether. The reaction pathway is confirmed by theoretical simulation, in which the crown ether acts as proton acceptor and shuttle to drive the formation and stabilization of carbamic acid. Improved CO2 capacity and diminished energy consumption in sorbent regeneration was achieved.

Ionic Pairs-Engineered Fluorinated Covalent Organic Frameworks Toward Direct Air Capture of CO2.

The covalent organic frameworks (COFs) possessing high crystallinity and capability to capture low-concentration CO2 (400 ppm) from air are still underdeveloped. The challenge lies in simultaneously incorporating high-density active sites for CO2 insertion and maintaining the ordered structure. Herein, a structure engineering approach is developed to afford an ionic pair-functionalized crystalline and stable fluorinated COF (F-COF) skeleton. The ordered structure of the F-COF is well maintained after the integration of abundant basic fluorinated alcoholate anions, as revealed by synchrotron X-ray scattering experiments. The breakthrough test demonstrates its attractive performance in capturing (400 ppm) CO2 from gas mixtures via O─C bond formation, as indicated by the in situ spectroscopy and operando nuclear magnetic resonance spectroscopy using 13C-labeled CO2 sources. Both theoretical and experimental thermodynamic studies reveal the reaction enthalpy of ≈-40 kJ mol-1 between CO2 and the COF scaffolds. This implies weaker interaction strength compared with state-of-the-art amine-derived sorbents, thus allowing complete CO2 release with less energy input. The structure evolution study from synchrotron X-ray scattering and small-angle neutron scattering confirms the well-maintained crystalline patterns after CO2 insertion. The as-developed proof-of-concept approach provides guidance on anchoring binding sites for direct air capture (DAC) of CO2 in crystalline scaffolds.

A PLC-based pomegranate sprout removal device design.

Aiming at the current low degree of mechanization of pomegranate sprouting tiller pruning in China, all relying on manual pruning, this paper designs a PLC-based pomegranate sprouting tiller removal machine. This machine adopts the identification method of wireless map transmission, the sprouting tiller removal method of multi-cylinder cooperative operation, and the MCGS configuration to realize the interaction between the user and the system, which realizes the displacement and angle compensation of the end-effector under complex conditions to realize the all-around accurate removal of the pomegranate sprouting tiller. The performance test and finite element analysis showed that the device could remove up to 74.62% of sprouting tillers, and the damage rate was as low as 18%. This meets the requirements of pomegranate plantations for the removal of emergent tillers.

Surpassing the Performance of Phenolate-derived Ionic Liquids in CO2 Chemisorption by Harnessing the Robust Nature of Pyrazolonates.

Superbase-derived ionic liquids (SILs) are promising sorbents to tackle the carbon challenge featured by tunable interaction strength with CO2 via structural engineering, particularly the oxygenate-derived counterparts (e. g., phenolate). However, for the widely deployed phenolate-derived SILs, unsolved stability issues severely limited their applications leading to unfavorable and diminished CO2 chemisorption performance caused by ylide formation-involved side reactions and the phenolate-quinone transformation via auto-oxidation. In this work, robust pyrazolonate-derived SILs possessing anti-oxidation nature were developed by introducing aza-fused rings in the oxygenate-derived anions, which delivered promising and tunable CO2 uptake capacity surpassing the phenolate-based SIL via a carbonate formation pathway (O-C bond formation), as illustrated by detailed spectroscopy studies. Further theoretical calculations and experimental comparisons demonstrated the more favorable reaction enthalpy and improved anti-oxidation properties of the pyrazolonate-derived SILs compared with phenolate anions. The achievements being made in this work provides a promising approach to achieve efficient carbon capture by combining the benefits of strong interaction strength of oxygenate species with CO2 and the stability improvement enabled by aza-fused rings introduction.

Incorporating Catalytic Units into Nanomaterials: Rational Design of Multipurpose Catalysts for CO2 Valorization.

ConspectusCO2 conversion to valuable chemicals is effective at reducing CO2 emissions. We previously proposed valorization strategies and developed efficient catalysts to address thermodynamic stability and kinetic inertness issues related to CO2 conversion. Earlier, we developed molecular capture reagents and catalysts to integrate CO2 capture and conversion, i.e., in situ transformation. Based on the mechanistic understanding of CO2 capture, activation, and transformation at a molecular level, we set out to develop heterogeneous catalysts by incorporating catalytic units into nanomaterials via the immobilization of active molecular catalysts onto nanomaterials and designing nanomaterials with intrinsic catalytic sites.In thermocatalytic CO2 conversion, carbonaceous and metal-organic framework (MOF)-based catalysts were developed for nonreductive and reductive CO2 conversion. Novel Cu- and Zn-based MOFs and carbon-supported Cu catalysts were prepared and successfully applied to the cycloaddition, carboxylation, and carboxylative cyclization reactions with CO2, generating cyclic carbonates, carboxyl acids, and oxazolidinones as respective target products. Reductive conversion of CO2, especially reductive functionalization with CO2, is a promising transformation strategy to produce valuable chemicals, alleviating chemical production that relies on petrochemistry. We explored the hierarchical reductive functionalization of CO2 using organocatalysts and proposed strategies to regulate the CO2 reduction level, triggering heterogeneous catalyst investigation. Introducing multiple active sites into nanomaterials opens possibilities to develop novel CO2 transformation strategies. CO2 capture and in situ conversion were realized with an N-doped carbon-supported Zn complex and MOF materials as CO2 adsorbents and catalysts. These nanomaterial-based catalysts feature high stability and excellent efficiency and act as shape-selective catalysts in some cases due to their unique pore structure.Nanomaterial-based catalysts are also appealing candidates for photocatalytic CO2 reduction (PCO2RR) and electrocatalytic CO2 reduction (ECO2RR), so we developed a series of hybrid photo-/electrocatalysts by incorporating active metal complexes into different matrixes such as porous organic polymers (POPs), metal-organic layers (MOLs), micelles, and conducting polymers. By introducing Re-bipyridine and Fe-porphyrin complexes into POPs and regulating the structure of the polymer chain, catalyst stability and efficiency increased in PCO2RR. PCO2RR in aqueous solution was realized by designing the Re-bipyridine-containing amphiphilic polymer to form micelles in aqueous solution and act as nanoreactors. We prepared MOLs with two different metallic centers, i.e., the Ni-bipyridine site and Ni-O node, to improve the efficiency for PCO2RR due to the synergistic effect of these metal centers. Sulfylphenoxy-decorated cobalt phthalocyanine (CoPc) cross-linked polypyrrole was prepared and used as a cathode, achieving the electrocatalytic transformation of diluted CO2 benefiting from the CO2 adsorption capability of polypyrrole. We fabricated immobilized 4-(t-butyl)-phenoxy cobalt phthalocyanine and Bi-MOF as cathodes to promote the paired electrolysis of CO2 and 5-hydroxymethylfurfural (HMF) and obtained CO2 reductive products and 2,5-furandicarboxylic acid (FDCA) efficiently.

Harnessing the Hybridization of a Metal-Organic Framework and Superbase-Derived Ionic Liquid for High-Performance Direct Air Capture of CO2.

Direct air capture (DAC) of CO2 has emerged as the most promising "negative carbon emission" technologies. Despite being state-of-the-art, sorbents deploying alkali hydroxides/amine solutions or amine-modified materials still suffer from unsolved high energy consumption and stability issues. In this work, composite sorbents are crafted by hybridizing a robust metal-organic framework (Ni-MOF) with superbase-derived ionic liquid (SIL), possessing well maintained crystallinity and chemical structures. The low-pressure (0.4 mbar) volumetric CO2 capture assessment and a fixed-bed breakthrough examination with 400 ppm CO2 gas flow reveal high-performance DAC of CO2 (CO2 uptake capacity of up to 0.58 mmol g-1 at 298 K) and exceptional cycling stability. Operando spectroscopy analysis reveals the rapid (400 ppm) CO2 capture kinetics and energy-efficient/fast CO2 releasing behaviors. The theoretical calculation and small-angle X-ray scattering demonstrate that the confinement effect of the MOF cavity enhances the interaction strength of reactive sites in SIL with CO2 , indicating great efficacy of the hybridization. The achievements in this study showcase the exceptional capabilities of SIL-derived sorbents in carbon capture from ambient air in terms of rapid carbon capture kinetics, facile CO2 releasing, and good cycling performance.

High-Performance CO2 Capture from Air by Harnessing the Power of CaO- and Superbase-Ionic-Liquid-Engineered Sorbents.

Direct air capture (DAC) of CO2 by solid porous materials represents an attractive "negative emission" technology. However, state-of-the-art sorbents based on supported amines still suffer from unsolved high energy consumption and stability issues. Herein, taking clues from the CO2 interaction with superbase-derived ionic liquids (SILs), high-performance and tunable sorbents in DAC of CO2 was developed by harnessing the power of CaO- and SIL-engineered sorbents. Deploying mesoporous silica as the substrate, a thin CaO layer was first introduced to consume the surface-OH groups, and then active sites with different basicities (e. g., triazolate and imidazolate) were introduced as a uniformly distributed thin layer. The as-obtained sorbents displayed high CO2 uptake capacity via volumetric (at 0.4 mbar) and breakthrough test (400 ppm CO2 source), rapid interaction kinetics, facile CO2 releasing, and stable sorption/desorption cycles. Operando diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS) analysis under simulated air atmosphere and solid-state NMR under 13 CO2 atmosphere demonstrated the critical roles of the SIL species in low-concentration CO2 capture. The fundamental insights obtained in this work provide guidance on the development of high-performance sorbents in DAC of CO2 by leveraging the combined advantages of porous solid scaffolds and the unique features of CO2 -philic ionic liquids.

Revolutionizing Porous Liquids: Stabilization and Structural Engineering Achieved by a Surface Deposition Strategy.

Facile approaches capable of constructing stable and structurally diverse porous liquids (PLs) that can deliver high-performance applications are a long-standing, captivating, and challenging research area that requires significant attention. Herein, a facile surface deposition strategy is demonstrated to afford diverse type III-PLs possessing ultra-stable dispersion, external structure modification, and enhanced performance in gas storage and transformation by leveraging the expeditious and uniform precipitation of selected metal salts. The Ag(I) species-modified zeolite nanosheets are deployed as the porous host to construct type III-PLs with ionic liquids (ILs) containing bromide anion , leading to stable dispersion driven by the formation of AgBr nanoparticles. The as-afforded type-III PLs display promising performance in CO2 capture/conversion and ethylene/ethane separation. Property and performance of the as-produced PLs can be tuned by the cation structure of the ILs, which can be harnessed to achieve polarity reversal of the porous host via ionic exchange. The surface deposition procedure can be further extended to produce PLs from Ba(II)-functionalized zeolite and ILs containing [SO4 ]2- anion driven by the formation of BaSO4 salts. The as-produced PLs are featured by well-maintained crystallinity of the porous host, good fluidity and stability, enhanced gas uptake capacity, and attractive performance in small gas molecule utilization.

Construction of Boron- and Nitrogen-Enriched Nanoporous π-Conjugated Networks Towards Enhanced Hydrogen Activation.

Boron-enriched scaffolds have demonstrated unique features and promising performance in the field of catalysis towards the activation of small gas molecules. However, there is still a lack of facile approaches capable of achieving high B doping and abundant porous channels in the targeted catalysts. Herein, construction of boron- and nitrogen-enriched nanoporous π-conjugated networks (BN-NCNs) was achieved via a facile ionothermal polymerization procedure with hexaazatriphenylenehexacarbonitrile [HAT(CN)6 ] sodium borohydride as the starting materials. The as-produced BN-NCN scaffolds were featured by high heteroatoms doping (B up to 23 wt. % and N: up to 17 wt. %) and permanent porosity (surface area up to 759 m2 g-1 mainly contributed by micropores). With the unsaturated bonded B species acting as the active Lewis acid sites and defected N species acting as the active Lewis base sites, those BN-NCNs delivered attractive catalytic performance towards H2 activation/dissociation in both gaseous and liquid phase, acting as efficient metal-free heterogeneous frustrated Lewis pairs (FLPs) catalysts in hydrogenation procedures.

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.

Construction of Fluorine- and Piperazine-Engineered Covalent Triazine Frameworks Towards Enhanced Dual-Ion Positive Electrode Performance.

Organic positive electrodes featuring lightweight and tunable energy storage modes by molecular structure engineering have promising application prospects in dual-ion batteries. Herein, a series of highly porous covalent triazine frameworks (CTFs) were synthesized under ionothermal conditions using fluorinated aromatic nitrile monomers containing a piperazine ring. Fluorinated monomers can result in more defects in CTFs, leading to a higher surface area up to 2515 m2 g-1 and a higher N content of 11.34 wt % compared to the products from the non-fluorinated monomer. The high surface area and abundant redox sites of these CTFs afforded high specific capacities (up to 279 mAh g-1 at 0.1 A g-1 ), excellent rate performance (89 mAh g-1 at 5 A g-1 ), and durable cycling performance (92.3 % retention rate after 500 cycles at 2.0 A g-1 ) as dual-ion positive electrodes.

CO2 Chemisorption Behavior in Conjugated Carbanion-Derived Ionic Liquids via Carboxylic Acid Formation.

Superbase-derived task-specific ionic liquids (STSILs) represent one of the most attractive and extensively studied systems in carbon capture via chemisorption, in which the obtained CO2 uptake capacity has a strong relationship with the basicity of the anions. High energy input in desorption and side reactions caused by the strong basicity of the anions are still unsolved issues. The development of other customized STSILs leveraging an alternative driving force to achieve efficient CO2 chemisorption/desorption is highly desirable yet challenging. In this work, carbanion-derived STSILs were developed for efficient CO2 chemisorption via a carboxylic acid formation pathway. The STSIL with the deprotonated malononitrile molecule ([MN]) as the anion exhibited much higher CO2 uptake capacity than the one derived from 2-methylmalononitrile ([MMN]). Notably, this trend was opposite to their basicity ([MN] < [MMN]). Detailed characterization of the products, supported by density functional theory simulations of spectra and calculations of the reaction energetics, demonstrated that carboxylic acid was formed upon reacting with CO2 via proton transfer in [MN]-derived STSILs but not in the case of [MMN] due to lack of an α-H. The preference of the carboxylic acid product over carboxylate formation was driven by the extended conjugation among the central sp2 carbon, the as-formed carboxylic acid, and the two nitrile groups. The achievements made in this work provide an alternative design principle of STSILs by leveraging the extended conjugation in the CO2-integrated product.

Molecular Engineering of Metal Complexes for Electrocatalytic Carbon Dioxide Reduction: From Adjustment of Intrinsic Activity to Molecular Immobilization.

The electrocatalytic CO2 reduction reaction (ECO2 RR) is one promising method for storing intermittent clean energy in chemical bonds and producing fuels. Among various kinds of catalysts for ECO2 RR, molecular metal complexes with well-defined structures are convenient for studies of their rational design, structure-reactivity relationships, and mechanisms. In this Review, we summarize the molecular engineering of several N-based metal complexes including Re/Mn bipyridine compounds and metal macrocycles, concluding with general modification strategies to devise novel molecular catalysts with high intrinsic activity. Through physical adsorption, covalent linking, and formation of a periodic backbone, these active molecules can be heterogenized into immobilized catalysts with more practical prospects. Finally, significant challenges and opportunities based on molecular catalysts are discussed.

Fully Conjugated Poly(phthalocyanine) Scaffolds Derived from a Mechanochemical Approach Towards Enhanced Energy Storage.

Phthalocyanines (Pc)-derived materials represent an attractive category of porous organic scaffolds featured by extensive π-conjugated networks, but their construction is still limited to the solution-based pathways, producing materials with inferior conductivity and porosity. Herein, a mechanochemistry-driven approach was developed leveraging the on-surface polymerization of aromatic nitrile monomers with ortho-positioned dicyano groups in the presence of metal catalysts (magnesium, zinc, or aluminum) under neat and ambient conditions. Diverse Pc-functionalized conjugated porous networks (Pc-CPNs) were obtained featured by extensively and fully π-conjugated skeletons, high surface areas, and hierarchical porosities. The monomers in this mechanochemical approach could be extended to those difficult to be handled in solution-based procedures. The Pc-CPNs displayed attractive electrochemical performance as supercapacitor and anodes in batteries, together with superb long-term stability.

Palladium-catalyzed carboxylative cyclization of propargylic amines with aryl iodides, CO2 and CO under ambient pressure.

A palladium-catalyzed four-component carboxylative cyclization comprising propargylic amines, aryl iodides, CO2 and CO was developed. By selecting Et3N and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the base, respectively, both terminal and internal propargylic amines proceeded well facilitated by Pd(PPh3)2Cl2, affording the functionalized 2-oxazolones in moderate yields. This protocol enlarges the product diversity based on CO2 conversion and simultaneously provides a cooperative transformation route for both CO2 and CO.

Highly Robust Rhenium(I) Bipyridyl Complexes Containing Dipyrromethene-BF2 Chromophores for Visible Light-Driven CO2 Reduction.

New rhenium bipyridyl complexes with dipyrromethene-BF2 chromophores (A-ReBDP-CZ, A-ReBDP2 , ReBDP-CZ, and ReBDP2 ) were developed for highly efficient photocatalytic carbon dioxide (CO2 ) reduction to carbon monoxide (CO). These catalysts consisted of two moderate electron-deficient groups (dipyrromethene-BF2 , BDP) as the visible-light-harvesting antenna as well as both electron donor (N-phenylcarbazole, CZ) and acceptor (BDP) on Re bipyridyl framework. Among ReBDP-CZ and ReBDP2 complexes, the ReBDP2 incorporating two electron-deficient BDP chromophores had a longer-lived photoexcited state (182.4 µs) and a twofold enhanced molar absorption coefficient (ϵ=157000 m-1 cm-1 ) compared with ReBDP-CZ. Thus, ReBDP2 achieved the superior photocatalytic reactivity and stability with a CO turnover number (TONCO ) value as high as 1323 and quantum yield (ΦCO ) up to 55 %, which was the most excellent photocatalysis efficiency among the single-active-site Re catalysts without additional photosensitizer. Furthermore, the acetylene-bridged linker was detrimental to the photoactivity and durability of the catalyst. In brief, two BDP-based Re bipyridyl systems with outstanding catalytic performance and significant visible-light-harvesting capabilities in the solar spectrum offer a promising strategy for solar-to-fuel conversion schemes.

Amphiphilic Polycarbonate Micellar Rhenium Catalysts for Efficient Photocatalytic CO2 Reduction in Aqueous Media.

A triblock amphiphilic polymer derived from the copolymerization of CO2 and epoxides containing a bipyridine rhenium complex in its backbone is shown to effectively catalyze the visible-light-driven reduction of CO2 to CO. This polymer provides uniformly spherical micelles in aqueous solution, where the metal catalyst is sequestered in the hydrophobic portion of the nanostructured micelle. CO2 to CO reduction occurs in an efficient visible-light-driven process in aqueous media with turnover numbers up to 110 (>99 % selectivity) in the absence of a photosensitizer, which is a 37-fold enhancement over the corresponding molecular rhenium catalyst in organic solvent. Notably, the amphiphilic polycarbonate micelle rhenium catalyst suppresses H2 generation, presumably by preventing deactivation of the active catalytic center by water.

Facile synthesis of α-aminophosphine oxides from diarylphosphine oxides, arynes and formamides.

The straightforward synthesis of α-amino phosphine oxides via three-component reactions involving arynes, formamides and diarylphosphine oxides is disclosed. This method employs the aryne to activate formamide, without an external activating reagent, which is operationally simple under mild conditions with high efficiency. Furthermore, mechanistic perception suggests a cascade sequence including formal [2 + 2] cycloaddition of the aryne with a CO bond, and a 1,4-addition of the H-P(O) compounds to the enamine intermediates.

Prolonging the Triplet State Lifetimes of Rhenium Complexes with Imidazole-Pyridine Framework for Efficient CO2 Photoreduction.

The photocatalytic reduction of CO2 into fuels offers the prospect for creating a new CO2 economy. Harnessing visible light-driven CO2 -to-CO reduction mediated by the long-lived triplet excited state of rhenium(I) tricarbonyl complexes is a challenging approach. We here develop a series of new mononuclear rhenium(I) tricarbonyl complexes (Re-1-Re-4) based on the imidazole-pyridine skeleton for photo-driven CO2 reduction. These catalysts are featured by combining pyridyl-imidazole with the aromatic ring and different pendant organic groups onto the N1 position of 1,3-imidazole unit, which display phosphorescence under Ar-saturated solution even at ambient conditions. By contrast, {Re[9-(pyren-1-yl)-10-(pyridin-2-yl)-9H-pyreno[4,5-d]imidazole)](CO)3 Cl} (Re-4) by introducing pyrene ring at the N1 position of pyrene-fused imidazole unit exhibits superior catalytic performance with a higher turnover number for CO (TONCO =124) and >99.9 % selectivity, primarily ascribed to the strong visible light-harvesting ability, long-lived triplet lifetimes (164.2 µs) and large reductive quenching constant. Moreover, the rhenium(I) tricarbonyl complexes derived from π-extended pyrene chromophore exhibit a long lifetime corresponding to its ligand-localized triplet state (3 IL) evidenced from spectroscopic investigations and DFT calculations.

Cu(II)-Catalyzed Phosphonocarboxylative Cyclization Reaction of Propargylic Amines and Phosphine Oxide with CO2.

Compounds bearing organophosphorus motifs and 2-oxazolidinone have found numerous applications in pharmaceutical chemistry, homogeneous catalysis, and organic materials. Here, we describe an efficient and selective protocol for straightforward access to a series of 5-((diarylphosphoryl)methyl)oxazolidin-2-ones via the copper-catalyzed difunctionalization of the C≡C bond of propargylic amines with CO2 and phosphine oxide. Notably, copper catalysis is a sustainable and benign catalytic mode. This reaction proceeds under mild reaction conditions, which is operationally simple and scalable with a broad scope, exclusive selectivity, and good functional group compatibility. Mechanistic studies suggest a one-pot tandem cyclization/radical addition sequence, along with the phosphorylation/cyclization scheme.