NEW CATALYTIC SYSTEMS FOR THE FIXATION OF CO_2 Ⅲ.INFLUENCE OF ADDITIVES AND REACTION MEDIUM ON THE COPOLYMERIZATION OF CARBON DIOXIDE-EPICHLOROHYDRIN IN THE PRESENCE OF Nd (P_(204))_3-Al(i-Bu)_3

Copolymerization of carbon dioxide with epichlorohydrin was successfully carried out by usingNd(P_(204))_3-Al(i-Bu)_3 as catalyst (P_(204))=(RO)_2 POO--,R=CH_3 (CH_2),CH(C_2H_5) CH_2--). Addi-tion of carbonyl compounds into the catalyst decreased the carbon dioxide content of the copoly-mer to some extent. Compared to nonpolar solvents, ethereal and moderate polar solvents werefavourable to obtaining higher carbon dioxide content copolymer. The coincidence of these resultswith the assumed copolymerization scheme clearly indicated that the copolymerization proceeds via coordinate anionic mechanism.

Carbon dioxide fixation by Chlorella sp.USTB-01 with a fermentor-helical combined photobioreactor

A promising microalgal strain isolated from fresh water,which can grow both autotrophically on inorganic carbon under lighting and heterotrophically on organic carbon without lighting,was identified as Chlorella sp.USTB-01 with the phylogenetic analysis based on 18S ribosomal ribonucleic acid(rRNA)gene sequences.In the heterotrophic batch culture,more than 20.0 g·L^(-1)of cell dry weight concentration(DWC)of Chlorella sp.USTB-01 was obtained at day 5,and which was used directly to seed the autotrophic culture.A novel fermentor-helical combined photobioreactor was established and used to cultivate Chlorella sp.USTB-01 for the fixation of carbon dioxide(CO_(2)).It showed that the autotrophic growth of Chlorella sp.USTB-01 in the combined photobioreactor was more effective than that in the fermentor alone and the maximum DWC of 2.5 g·L^(-1)was obtained at day 6.The highest CO_(2)fixation of 95%appeared on day 1 in the exponential growth phases of Chlorella sp.USTB-01 and 49.8%protein was found in the harvested microalgal cells.

Recent Advances on Metal-Organic Frameworks in the Conversion of Carbon Dioxide

With the development of modern industry,global warming is becoming a challenging issue due to the emissions of large quantities of greenhouse gases,mainly carbon dioxide(CO_(2)).The conversion of CO_(2)to useful compounds is considered as an effective and economic way to solve such a climate problem.Metal-organic frameworks(MOFs)are an emerging class of porous crystalline materials that have shown great potential in the conversion of CO_(2).The advantages of MOFs in CO 2 conversion lie in their high surface areas,adjustable pore size,and high porosity.More importantly,desirable functional sites can be easily designed and precisely installed to the pore wall of target MOFs by pre-assembly and/or post-synthetic modification(PSM)ways.This review summarizes the recent advances in constructing MOF catalysts for the application in CO_(2)conversion.We believe that the design and synthesis of MOF catalysts for CO_(2)conversion can be a promising way to solve the“greenhouse effect”.

Combination of binary active sites into heterogeneous porous polymer catalysts for efficient transformation of CO_(2) under mild conditions

The transformation of CO_(2)into cyclic carbonates via atom-economical cycloadditions with epoxides has recently attracted tremendous attention.On one hand,though many heterogeneous catalysts have been developed for this reaction,they typically suffer from disadvantages such as the need for severe reaction conditions,catalyst loss,and large amounts of soluble co-catalysts.On the other hand,the development of heterogeneous catalysts featuring multiple and cooperative active sites,remains challenging and desirable.In this study,we prepared a series of porous organic catalysts(POP-PBnCl-TPPMg-x)via the copolymerization metal-porphyrin compounds and phosphonium salt monomers in various ratios.The resulting materials contain both Lewis-acidic and Lewis-basic active sites.The molecular-level combination of these sites in the same polymer allows these active sites to work synergistically,giving rise to excellent performance in the cycloaddition reaction of CO_(2)with epoxides,under mild conditions(40℃ and 1 atm CO_(2))in the absence of soluble co-catalysts.POP-PBnCl-TPPMg-12 can also efficiently fixate CO_(2)under low-CO_(2)-concentration(15%v/v N2)conditions representative of typical CO_(2)compositions in industrial exhaust gases.More importantly,this catalyst shows excellent recyclability and can easily be separated and reused at least five times while maintaining its activity.In view of their heterogeneous nature and excellent catalytic performance,the obtained catalysts are promising candidates for the transformation of industrially generated CO_(2)into high value-added chemicals.

Polystyrene-supported Phenol/DMAP： an Efficient Binary Catalyst System for CO2 Fixation to Give Cyclic Carbonates

Polystyrene-supported phenol （PS-PhOH） was successfully synthesized by alkylation reaction of phenol with 2% DVB cross-linked chloromethylated polystyrene and characterized by IR spectra and elemental analysis. In conjunction with an organic base such as DMAP, DBU, triethylamine （Et3N）, diethylamine （Et2NH） or pyridine, the PS-PhOH could effectively catalyze the coupling reaction of carbon dioxide with epoxides to give cyclic carbonates in high yield and selectivity under mild conditions. The binary catalyst system of the PS-PhOH/DMAP was found to be the most active. The influence of reaction temperature, carbon dioxide pressure and reaction time on the yield of product was carefully investigated. The PS-PhOH could be recycled by simple filtration for at least up to ten times without loss of catalytic activity.

Chiral basket-handle porphyrin-Co complexes for the catalyzed asymmetric cycloaddition of CO_2 to epoxides

The catalytic synthesis of cyclic carbonates via the cycloaddition of CO2 to epoxides is a standard methodology for CO2 fixation.For this purpose,chiral basket-handle porphyrin-Co complexes were devised,prepared,and fully characterized by nuclear magnetic resonance,mass spectrometry,Fourier transform infrared spectroscopy,ultraviolet-visible spectroscopy,and specific rotation.The proposed metalloporphyrin catalysts were synthesized with either 1,1'-bi-2-naphthol or L-phenylalanine,which have different chirality,and then applied to the coupling of propylene oxide and CO2 for generating chiral cyclic carbonates with good enantioselectivity under extremely mild conditions in the presence of tetrabutyl ammonium chloride as a co-catalyst.The good enantioselectivity in the cycloaddition reaction is attributed to a synergistic interplay between the chiral porphyrin catalysts and the substrate.The mechanism and enantioselectivity of the asymmetric cycloaddition reaction is discussed.

DBU-Mediated Carboxylative Coupling of Primary Amines,Carbon Dioxide and Propargyl Chlorides

A carboxylative coupling reaction of various primary amine and 3-phenyl-2-propynyl or 2-nonynyl chloride in the presence of 8-diazabicyclo[5.4.0]undec-7-ene(DBU)using carbon dioxide as carboxylative reagent was presented.This transition-metal free reaction system shows broad substrate scope and gives a series of propargylcarbamates in moderate to good yield.The obtained N-alkyl substituted carbamate product can undergo base-catalyzed intramolecular cyclization reaction to afford functionalized 4-methylene-2-oxazolidinone in good yield.

Silver-Catalyzed Three-Component Coupling of Carbon Dioxide, Amines and α-Diazoesters

A silver-catalyzed three-component coupling reaction of carbon dioxide, amines and α-diazoesters has been developed for the first time. The novel reaction provides an efficient and practical methodology for the synthesis of a wide range of new α-carbamoyloxy esters, which are difficult to prepare by existing methods. The advantages of the method include the use of readily available starting materials, simple catalytic system, good atom economy and high functional group tolerance.

Subcloning and Sequencing of the Form II Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase from Rhodopseudomonas palustris

Rhodopseudomonas palustris, one of purple nonsulfur photosynthetic bacteria, fixes carbon dioxide via Calvin-Benson cycle and has been shown previously to express form I and form II ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO). The gene cbbM, which encodes the form II enzyme from Rhodopseudomonas palustris, has been subcloned and sequenced. The deduced amino acid sequence is highly with the form II RubisCO from photosynthetic bacteria, including Rhodospirillum rubrum (PDB ID: 9rub), but appears to be more distantly related to the large subunit of the form I RubisCO found in photosynthetic bacteria, chemoautotrophic bacteria and higher plants. Several regions highly conserved among L 8S 8 and L x enzymes correspond with regions previously implicated in catalytic activity and subunit interactions.

Realizing Stable Carbonate Electrolytes in Li-O_(2)/CO_(2)Batteries

The increasing demand for high-energy storage systems has propelled the development of Li-air batteries and Li-O_(2)/CO_(2)batteries to elucidate the mechanism and extend battery life.However,the high charge voltage of Li2CO3 accelerates the decomposition of traditional sulfone and ether electrolytes,thus adopting high-voltage electrolytes in Li-O_(2)/CO_(2)batteries is vital to achieve a stable battery system.Herein,we adopt a commercial carbonate electrolyte to prove its excellent suitability in Li-O_(2)/CO_(2)batteries.The generated superoxide can be captured by CO_(2)to form less aggressive intermediates,stabilizing the carbonate electrolyte without reactive oxygen species induced decomposition.In addition,this electrolyte permits the Li metal plating/stripping with a significantly improved reversibility,enabling the possibility of using ultra-thin Li anode.Benefiting from the good rechargeability of Li2CO3,less cathode passivation,and stabilized Li anode in carbonate electrolyte,the Li-O_(2)/CO_(2)battery demonstrates a long cycling lifetime of 167 cycles at 0.1 mA·cm^(-2)and 0.25 mAh·cm^(-2).This work paves a new avenue for optimizing carbonate-based electrolytes for Li-O_(2)and Li-O_(2)/CO_(2)batteries.

Iron and lead ion adsorption by microbial flocculants in synthetic wastewater and their related carbonate formation

Although microbial treatments of heavy metal ions in wastewater have been studied, the removal of these metals through incorporation into carbonate minerals has rarely been reported. To investigate the removal of Fe^3＋ and Pb^2＋, two representative metals in wastewater, through the precipitation of carbonate minerals by a microbial flocculant （MBF） produced by Bacillus mucilaginosus. MBF was added to synthetic wastewater containing different Fe^3＋ and Pb^2＋ concentrations, and the extent of flocculation was analyzed. CO2 was bubbled into the mixture of MBF and Fe^3＋/Pb^2＋ to initiate the reaction. The solid substrates were analyzed via X-ray diffraction, transmission electron microscopy and energy dispersive spectroscopy. The results showed that the removal efficiency decreased and the MBF adsorption capacity for metals increased with increasing heavy metal concentration. In the system containing MBF, metals （Fe^3＋ and Pb^2＋）, and CO2, the concentrated metals adsorbed onto the MBF combined with the dissolved CO2, resulting in oversaturation of metal carbonate minerals to form iron carbonate and lead carbonates. These results may be used in designing a method in which microbes can be utilized to combine CO2 with wastewater heavy metals to form carbonates, with the aim of mitigating environmental problems.

Synthetic biology for CO2 fixation

Recycling of carbon dioxide(CO_2) into fuels and chemicals is a potential approach to reduce CO_2 emission and fossil-fuel consumption. Autotrophic microbes can utilize energy from light, hydrogen, or sulfur to assimilate atmospheric CO_2 into organic compounds at ambient temperature and pressure. This provides a feasible way for biological production of fuels and chemicals from CO_2 under normal conditions. Recently great progress has been made in this research area, and dozens of CO_2-derived fuels and chemicals have been reported to be synthesized by autotrophic microbes. This is accompanied by investigations into natural CO_2-fixation pathways and the rapid development of new technologies in synthetic biology. This review first summarizes the six natural CO_2-fixation pathways reported to date, followed by an overview of recent progress in the design and engineering of CO_2-fixation pathways as well as energy supply patterns using the concept and tools of synthetic biology. Finally, we will discuss future prospects in biological fixation of CO_2.

Artificial and Semi-artificial Photosynthesis(AP and SAP)Systems Based on Metal-Organic Frameworks

Recently,artificial and semi-artificial photosynthesis have attracted extensive attentions in addressing the crisis of energy from fossil fuels and reducing excessive CO_(2) emission.Metal-organic frameworks(MOFs)have been considered as ideal platforms for constructing artificial photosynthesis systems due to their unique properties like large specific surface area,high porosity and diverse framework topology,and tunable functionalities.This review discussed the characteristics,superiorities and challenges of MOF-based photocatalysts,and detailed summarization of several common design strategies for MOF-based artificial systems,including i)enhancement of light absorption,ii)acceleration of the charge separation and transfer,and iii)introduction of additional active units.Particularly,we give examples showing the applications of MOF-based photocatalysts,where the mechanisms of superior photocatalytic activity and selectivity are also analyzed,thereby providing theoretical guidance for rational design of MOF-based photocatalysts.Finally,the challenges and future research directions of MOF-based photocatalysts are prospected.

Photocatalytic Carboxylation of Phenyl Halides with CO_(2) by Metal-Organic Frameworks Materials

In this work,important commercial pharmaceutical intermediates,phenylpropionic acid compounds,are successfully obtained by catalyzing the reaction of carbon dioxide with phenyl halides using MOF-5,a typical metal-organic framework(MOF)material.The influence of temperature,pressure,catalyst type and light on the reaction is investigated,and a 90.3%selectivity towards fluorophenylpropionic acid is reached.Significantly,the catalysts are effective for varied benzyl compounds containing different substituent groups.The catalysts are stable and remain active after three cycles.

Enantioselective Resolution Copolymerization of Racemic 2,3-Disubstituted cis-Epoxides with CO_(2) Mediated by Binuclear Cobalt(Ⅲ)Catalyst

Enan tioselective resoluti on copolymerization of racemic internal epoxides with carb on dioxide(CO_(2))is a challe nging issue because of their poor reactivity and complicated regio/stereoselectivity.Herein,we describe the first enantioselective resolution copolymeriza-tion of racemic aromatic 2,3-disubstituted c/s-epoxides and CO_(2) using enantiopure dinuclear cobalt(lll)complexes as catalyst under mild conditions,affordi ng the corresp on ding polycarbonates with completely alter nating structure and good enantioselectivity in the range of 70% to 97%ee.The isotactic polycarb on ate from/3-methylstyre ne oxide is a typical semicrystalli ne material,possessi ng a melting point of 241℃;while other isotactic-enriched copolymers from 2,3-disubstituted c/s-epoxides bearing a substitute group on the aromatic ring are amorphous,having glass transition temperatures between 86℃ and 124℃.Interestingly,the copolymer selectivity is correlated well with the Hammett substituent constant,and the highest polymer selectivity of 98%was found in the system using the epoxides bearing an electron-donating group on the benzene ring.

Palladium-Catalyzed Cyclization Reaction of o-Haloanilines, CO2 and Isocyanides： Access to Quinazoline-2,4（1H,3H）-diones

Quinazoline-2,4（1H,3H）-diones are core structural subunits frequently found in many biologically important compounds. The reaction of 2- aminobenzonitrile and CO2, which was frequently studied, only provided N3-unsubstituted quinazoline-2,4（1H,3H）-dione compounds. Herein we report palladium-catalyzed cyclization reactions of o-haloanilines, CO2 and isocyanides to prepare N3-substituted quinazoline-2,4（1H,3H）-diones. Electron-rich o-bromoanilines participated in the cyclization reaction using Cs2CO3 at high temperature, and electron-deficient o-bromoaniline or o-iodoaniline sub- strates conducted the reaction using CsF as base to deliver corresponding quinazoline-2,4（1H,3H）-dione products in good yields.

Hydroxyl Group-Enabled Highly Efficient Ligand for Pd-Catalyzed Telomerization of 1,3-Butadiene with CO_(2)

By introducing hydroxyl group into PPh3 ligand,a promoter-free palladium catalytic system based on(p-HOC6H4)PPh2 ligand was developed for the telomerization of 1,3-butadiene with CO_(2).High activity and selectivity towards CO_(2)-incorporated divinylδ-lactone monomer were achieved(TON/TOF:up to 4540/568 h–1;selectivity ofδ-lactone and its isomers:up to 97%).The key role of phenolic hydroxyl group of the ligand in attaining high activity was validated.The good performance of large-scale reaction in batch reactor demonstrated the potential utility of this simple catalytic system in valorizing CO_(2) with bulk chemical feedstock.

Distribution characteristics and diversities of cbb and coxL genes in paddy soil profiles from southern China

The Calvin-Benson-Bassham cycle and Wood-Ljungdahl pathway are two well-known ones in the six carbon sequestration pathways,but the current knowledge of their occurrence in different layers of agricultural soil profiles is poor.In this study,the diversities of three genes encoding ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubis CO),i.e.,genes encoding the green-like(cbbLG)and red-like(cbbLR)forms of Rubis COⅠ and encoding Rubis COⅡ(cbbM),and the gene encoding carbon monoxide dehydrogenase large subunit(coxL)from five paddy soils in southern China were investigated by real-time quantitative polymerase chain reaction,restriction fragment length polymorphism(RFLP)analysis,and clone library.The abundances of the four genes ranged from 10^(7) to 10^(9) copies g^(-1) soil,and the cbbLR gene outnumbered the other three genes in all soil samples,suggesting important roles they play in carbon dioxide(CO_(2))fixation.In addition,it was found that the copy numbers of cbbLR and cbbLG decreased with increasing soil depth,while the copy numbers of cbbM and coxL decreased in the shallow depths but increased with increasing soil depth.The results of RFLP showed a larger Shannon index(H)in the deeper soil layers among the four gene clone libraries,indicating that the community diversity in these soil layers was greater.The cbbLG gene had relatively low diversity(at genus level),and most of the sequences were classified as Sideroxydans and Thiobacillus.In contrast,the highly diverse groups were found in the other three gene clone libraries(cbbLR,cbbM,and coxL),most of which were distantly related to known sequences,even forming separate clusters.In summary,this study provides a new insight into CO_(2) fixers along agricultural soil profiles by comparing four bacterial genes.