Enabling heterogeneous catalysis to achieve carbon neutrality: Directional catalytic conversion of CO_(2) into carboxylic acids

The increase in anthropogenic carbon dioxide(CO_(2))emissions has exacerbated the deterioration of the global environment,which should be controlled to achieve carbon neutrality.Central to the core goal of achieving carbon neutrality is the utilization of CO_(2) under economic and sustainable conditions.Recently,the strong need for carbon neutrality has led to a proliferation of studies on the direct conversion of CO_(2) into carboxylic acids,which can effectively alleviate CO_(2) emissions and create high-value chemicals.The purpose of this review is to present the application prospects of carboxylic acids and the basic principles of CO_(2) conversion into carboxylic acids through photo-,electric-,and thermal catalysis.Special attention is focused on the regulation strategy of the activity of abundant catalysts at the molecular level,inspiring the preparation of high-performance catalysts.In addition,theoretical calculations,advanced technologies,and numerous typical examples are introduced to elaborate on the corresponding process and influencing factors of catalytic activity.Finally,challenges and prospects are provided for the future development of this field.It is hoped that this review will contribute to a deeper understanding of the conversion of CO_(2) into carboxylic acids and inspire more innovative breakthroughs.

Two New Phenolic Carboxylic Acid Esters from Opuntia vulgaris

Two new phenolic carboxylic acid esters n-butyl eucomate(1) and methyl eucomate (2) and six known compounds eucomic acid(3), 3-β-acetyl-taraxerol (4), friedelin(5),lupenone(6),methyl linoleate(7) and methyl oleate(8) were isolated from the stems of Opuntia vulgaris Mill(Cactaceae). Their structures were determined on the basis of spectral methods. Compounds 3,4,6,7,8 were isolated for the first time from this plant.

Sensitive Voltammetric Determination of Captopril Using a Carbon Paste Electrode Modified with Nano-TiO_2/Ferrocene Carboxylic Acid

A carbon paste electrode (CPE) modified with ferrocene carboxylic acid (FcCA) and TiO2 nanoparticles was constructed by incorporating TiO2 nanoparticles and ferrocene carboxylic acid into the carbon paste matrix. The electrochemical behavior of captopril (CAP) at the surface of the modified electrode was investigated using electroanalytical methods. The modified electrode showed excellent electrocatalytic activity for the oxidation of CAP in aqueous solutions at physiological pH values. Cyclic voltammetric curves showed that the oxidation of CAP at the surface of the modified electrode reduced its overpotential by more than 290 mV. The modified electrode was used for detecting captopril using cyclic voltammetry and square wave voltammetry techniques. A calibration curve in the range of 0.03 to 2400 μmol/L was obtained that had a detection limit of 0.0096 μmol/L (3?) under the optimized conditions. The modified electrode was successfully used for the determination of captopril in pharmaceutical and biological samples.

Sulfonated carbon catalyzed oxidation of aldehydes to carboxylic acids by hydrogen peroxide

Sulfonated carbon as a strong and stable solid acid catalyst exhibited excellent catalytic performance in various acid-catalyzed reactions. Here, sulfonated carbon, as catalyst for oxidation reaction, was prepared via the carbonization of starch followed by sulfonation with concentrated sulfuric acid. N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray fluorescence and acid-base titration were used to characterize the obtained materials. The catalytic activity of sulfonated carbon was studied in the oxidation of aldehydes to carboxylic acids using 30 wt% H2O2 as oxidant. This oxidation protocol works well for various aldehydes including aromatic and aliphatic aldehydes. The sulfonated carbon can be recycled for three times without obvious loss of activity.

Efficient Fixation of Carbon Dioxide by Electrolysis——Facile Synthesis of Useful Carboxylic Acids

Electrochemical fixation of atmospheric pressure of carbon dioxide to organic compounds is a useful and attractive method for synthesizing of various carboxylic acids. Electrochemical fixation of carbon dioxide, electrochemical carboxylation, organic halides, organic triflates, alkenes, aromatic compounds, and carbonyl compounds can readily occur in the presence of an atmospheric pressure of carbon dioxide to form the corresponding carboxylic acids with high yields, when a sacrificial anode such as magnesium or aluminum is used in the electrolysis. The electrochemical carboxylation of vinyl bromides was successfully applied for the synthesis of the precursor of nonsteroidal anti-inflammatory agents such as ibuprofen and naproxen. On the other hand, supercritical carbon dioxide （scCO2） has significant potential as an environmentally benign solvent in organic synthesis and it could be used both as a solvent and as a reagent in these electrochemical carboxylations by using a small amount of cosolvent.

Comparison of Carboxylic Acids in Some Crude Oils and Their Diesel Distillates and VGOs:Characterized by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (Negative-Ion ESI FT-ICR MS)

Three high-acidity crudes, Dar, SZ36-1, and QHD326, were separated through distillation into several fractions, including diesel distillates, and VGOs. Samples were characterized by negative-ion ESI FT-ICR MS. The O2 class species （petroleum carboxylic acids）, which have a close relationship with corrosion of equipment caused by high-acidity crudes, were put in the focus of attention and were discussed in this paper. Monocyclic, bicyclic, and tricyclic naphthenic acids are the main types of petroleum carboxylic acids in naphthenic-base crudes （SZ36-1 and QHD326）. But the main types of petroleum carboxylic acids in paraffinic-base crude （Dar） are aliphatic acids and monocyclic naphthenic acids. The O2 class species in SZ36-1 and QHD326 are distributed in a wider range and have bigger DBE value （double-bond equivalence value） and carbon number than Dar. Bicyclic naphthenic acids have the highest proportion among petroleum carboxylie acids in diesel distillates, but monocyclic and tricyclic naphthenic acids also occupy a high proportion. Particularly, aliphatic acids in the diesel distillate of Dar still have high proportion among petroleum carboxylic acids. The distribution of petroleum carboxylic acids in VGO is basically identical. The bicyclic naphthenic acids assume the first place （about 25 m%）, while the monocyclic and tricyclic naphthenic acids take the next place. The comparison of petroleum carboxylic acids in diesel distillates and VGOs has revealed that the molecules of carboxylic acids in VGOs are not only bigger but also more complicated.

Reductive Conversion of Biomass-Derived Furancarboxylic Acids with Retention of Carboxylic Acid Moiety

Catalytic reduction systems of 2-furancarboxylic acid(FCA)and 2,5-furandicarboxylic acid(FDCA)with H 2 without reduction of the carboxyl groups are reviewed.FCA and FDCA are produced from furfural and 5-hydroxymethylfurfural which are important platform chemicals in biomass conversions.Furan ring hydrogenation to tetrahydrofuran-2-carboxylic acid(THFCA)and tetrahydrofuran-2,5-dicarboxylic acid(THFDCA)easily proceeds over Pd catalysts.Hydrogenolysis of one C–O bond in the furan ring produces 5-hydroxyvaleric acid(5-HVA)and 2-hydroxyadipic acid.2-Hydroxyvaleric acid is not produced in the reported systems.5-HVA can be produced as the lactone form(δ-valerolactone;DVL)or as the esters depending on the solvent.These reactions proceed over Pt catalysts with good yields(~70%)at optimized conditions.Hydrogenolysis of two C–O bonds in the furan ring produces valeric acid and adipic acid,the latter of which is a very important chemical in industry and its production from biomass is of high importance.Adipic acid from FDCA can be produced directly over Pt-MoO_(x) catalyst,indirectly via hydrogenation and hydrodeoxygenation as one-pot reaction using the combination of Pt and acid catalysts such as Pt/niobium oxide,or indirectly via two-step reaction composed of hydrogenation catalyzed by Pd and hydrodeoxygenation catalyzed by iodide ion in acidic conditions.Only the two-step method can give good yield of adipic acid at present.

Syntheses,Crystal Structures and Antibacterial Activities of 5-Chloro-3-methyl-1-phenyl-1H-pyrazole-4-carboxylic Acid and Its Copper(Ⅱ) Compound

The title compounds 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid（C11H9Cl N2O2, HL）（1） and [Cu（L）2（H2O）]（2） were prepared and structurally characterized by elemental analysis, IR and single-crystal X-ray diffraction. Compound 1（C11H9Cl N2O2） crystallizes in the monoclinic system, space group P21/n with a = 7.249（3）, b = 20.515（10）, c = 7.249（3）,β= 96.30°, V = 1071.6（9） ？3, Z = 4, Mr = 236.65, Dc = 1.467 g/cm3, F（000） = 488, GOOF = 1.029, μ= 0.341 mm-1, the final R = 0.0736 and w R = 0.1966 for 1500 observed reflections with I 〉 2σ（I）. Compound 2（C22H18Cl2Cu N4O5） crystallizes in the monoclinic system, space group P21/c with a = 7.2931（6）, b = 24.548（2）, c = 13.2726（11）, β= 99.4040（10）°, V = 2344.2（3） ？3, Z = 4, Mr = 552.84, Dc = 1.566 g/cm3, F（000） = 1124, GOOF = 1.050, μ= 1.201 mm-1, the final R = 0.0376 and w R = 0.1000 for 3626 observed reflections with I 〉 2σ（I）. 1 and 2 are connected through hydrogen bonding interactions to generate 2D and 3D supramolecular structures, respectively. Moreover, the preliminary antibacterial activities of 1 and 2 against the gram positive bacteria（S. aureus, C. albicans and B. subtilis） and gram negative bacteria（E. coli and P. aeruginosa） have been tested by using the microdilution method, and the results indicate that 2 is more active than 1 against the tested bacteria.

Synthesis and Properties of Ternary Europium Complexes with Aromatic Carboxylic Acid and Nitrogen-Containing Heterocyclic Ligand

Seven ternary Eu （m） complexes were synthesized with aromatic carboxylic acid （benzoic acid, phenylacetic acid, phenylpropionic acid and cinnamic acid） as the first ligand and 1,10-phenanthro- line or 2,2＇-dipyridyl as the second ligand. The ternary Eu（ Ⅲ ） complexes were characterized by elemental analysis, IR and TG-DTG methods. In these complexes, the Eu （Ⅲ） ions are bonded to the oxygen atoms of carboxylate and the nitrogen atoms of neutral ligands. Four complexes whose second ligand is 1,10- phenanthrolin have fine thermal stability. Excitation and luminescence spectra of the tide complexes reveal that the fluorescence of the complexes in which 1,10- phenanthrolin as the second ligand are more intensive than those complexes in which 2, 2＇-dipyridyl as the second ligand. The order of the strongest emission peak of seven ternary complexes is： Eu（β-PPA）3phen 〉 Eu（BA）3phen 〉 Eu（PLA）3phen 〉 Eu（BA）3bipy 〉 Eu （ PEA）3bipy 〉 Eu （ CA ）3phen · H2O 〉 Eu （ CA ）3bipy （BA ： benzoic ; PEA ： phenylacetic ; β-PPA ：

Robust cobalt oxide catalysts for controllable hydrogenation of carboxylic acids to alcohols

The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production,while efficient heterogeneous catalyst systems are still being explored.Here,we report the selective hydrogenation of carboxylic acids using earth‐abundant cobalt oxides through a reaction‐controlled catalysis process.The further reaction of the alcohols is completely hindered by the presence of carboxylic acids in the reaction system.The partial reduction of cobalt oxides by hydrogen at designated temperatures can dramatically enhance the catalytic activity of pristine samples.A wide range of carboxylic acids with a variety of functional groups can be converted to the corresponding alcohols at a yield level applicable to large‐scale production.Cobalt monoxide was established as the preferred active phase for the selective hydrogenation of carboxylic acids.

Theoretic Simulation of Pr^(3+) and Nd^(3+) Complexes with αHydroxyl Carboxylic Acids

The potential energy difference of trivalent Pr/Nd complex ions with various α hydroxyl carboxylic acids were computed by molecular mechanics plus(MM +) model. Its relationships with the steric hindrance of the coordinating lignads and with the separation factor of Pr/Nd were discussed. It is found that the MM + model can be used for selecting and designing ligand as effective eluant, with which Pr 3+ and Nd 3+ can be separated by ion exchange chromatography.

Long-chain alkanol-alkyl carboxylic acid-based low-viscosity hydrophobic deep eutectic solvents for one-pot extraction of anthraquinones from Rhei Radix et Rhizoma

Natural long-chain alkanol and alkyl carboxylic acid were used to prepare novel hydrophobic deep eutectic solvents(HDESs).These HDESs are liquid at room temperature and have low viscosity(<12.26 mPa·s),low polarity(lower than that of methanol,ChCl-based deep eutectic solvents and other reported HDESs),and low density(<0.928 g/mL).A simple one-pot method based on a novel HDES-water two-phase extraction system was constructed for the extraction of weak-polarity bioactive components,anthraquinones,from Rhei Radix et Rhizoma.This HDES-based new extraction method does not consume hazardous organic solvents and can obtain a total anthraquinone yield of 21.52 mg/g,which is close to that obtained by the Chinese pharmacopoeia method(21.22 mg/g)and considerably higher than those by other reported HDESs-based extraction methods(14.20-20.09 mg/g,p<0.01).The high extraction yield can be mainly attributed to the severe destruction of the RRR cell walls by the extraction system and the excellent dissolving ability of novel HDESs for anthraquinones.

Boosting chiral carboxylic acid hydrogenation by tuning metal-MO_(x)-support interaction in Pt-ReO_(x)/TiO_(2) catalysts

Engineering the surface microenvironment by tuning the binary interactions between a supported metal with a secondary metal oxide(MO_(x))or support has been a common method for improving the catalytic performance of supported metal catalysts.However,few studies have investigated the ternary interactions among the metal,MO_(x),and support.Here,we report for the first time the formation of metal-MO_(x)-support interaction(MMSI)in reducible TiO_(2)-supported PtReO_(x) catalysts,affording 87% yield and 100% ee in the tandem hydrogenation of an aqueous chiral cyclohexane-1,2-dicarboxylic acid into the corresponding diol;the catalytic activity is eight times higher than that obtained with non-reducible support counterparts in the same reaction via traditional batch synthesis with multiple steps and unfriendly reagents.Detailed experimental and computational studies suggest that the TiO_(2) crystalline phase-dependent density of the oxygen vacancies induces different Pt-ReO_(x)-TiO_(2) interactions,which dominate the electron transfer therein and tune the adsorption strength of the carbonyl moiety of the substrate/intermediate,thus promoting the hydrogenation activity and selectivity.In addition,the strong MMSI endows the optimal rutile TiO_(2) supported PtReO_(x) catalyst with an outstanding lifetime of 400 h in a fixed-bed reactor under acidic aqueous conditions and ensures efficient applications in the selective hydrogenation of aliphatic dicarboxylic acids and functional carboxylic acids.This work provides a promising strategy for the development of efficient and stable supported catalysts for the selective hydrogenation of diverse C-O and C=O bonds.

On-line Preconcentration and Determination of Trace Metals in Water Samples by Flow Injection Combined with Flame Atomic Absorption Spectrometry via Calix[4]arene Carboxylic Acid Packed Micro-column

An adsorbent calix[4]arene carboxylic acid was employed as the adsorption material for on-line flow in jection（FI） micro-column preconcentration coupled with flame atomic absorption spectrometry（FAAS） determination of trace heavy metals（Cu, Pb, Co, Ni and Cd）. Parameters such as the pH, loading time and flow rate of sample, and the concentration, volume and flow rate of eluent were optimized. The enrichment factors are 50.0, 56.5, 11.6, 12.1 and 19.1 for Cu, Pb, Co, Ni, and Cd, respectively, and a sample throughput of 20 h–1 was obtained. The limits of de tection for Cu, Pb, Co, Ni, and Cd were in a range of 1.56―3.91 μg/L, and the relative standard deviations（RSDs） were less than 2.76%（n=7）. Furthermore, the proposed method was successfully applied to the determination of Cu, Pb, Co, Ni, and Cd in certified reference materials and various water samples.

Distribution of Carboxylic Acids in Sudanese Dar Crude Oil: Characterized by Negative-Ion Electrospray Ionization Fou- rier Transform Ion Cyclotron Resonance Mass Spectrometry

The Dar crude oil produced in Sudan was distilled into several fractions. The heteroatom class species in crude and its fractions were characterized by the negative-ion ESI FT-ICR MS. The major emphasis was put upon the study on the O2 class species (petroleum carboxylic acids). The test results revealed that aliphatic acids and monocyclic naphthenic acids accounted for a large proportion in petroleum carboxylic acids of the Dar crude. The relative abundance of aliphatic acids and monocyclic naphthenic acids decreased with an increasing boiling point of fractions. Meanwhile, the relative abundance of bicyclic and tricyclic naphthenic acids increased at first and then decreased, whereas the relative abundance of petroleum carboxylic acids with higher double-bond equivalence (DBE) values increased. The high abundance of aliphatic acids in the Dar crude and its fractions covered the carbon numbers in a range of 16 to 18 which had important geochemical signifi- cance. The O2 class species were distributed in a broad range of DBE values and carbon numbers with increasing boiling points of fractions.

Synthesis and Crystal Structure of 4-(4,6-dimethoxyl -pyrimidin-2-yl)-3-thiourea Carboxylic Acid Methyl Ester

The title compound 4-（4,6-dimethoxylpyrimidin-2-yl）-3-thiourea carboxylic acid methyl ester was synthesized by the reaction of 2-amino-4,6-dimethoxyl pyrimidine, potassium thiocyanate and methyl chloroformate in ethyl acetate. Single crystals suitable for X-ray measurement were obtained by recrystallization with the solvent of dimethyl formamide at the room temperature. The structure was characterized by elemental analysis and IR and determined by X-ray diffraction analysis＇ Crystallographic data： C9H12N4O4S, Mr = 272.29, monoclinic, space group C2/m with a = 1.6672（3）, b = 0.66383（12）, c = 1.1617（2） nm, β = 109.275（2）°, V = 1.2136（4） nm^3, Dc = 1.490 g/cm^3,μ = 0.281 mm^-1, F（000） = 568, Z = 4, R1 = 0.0341and wR2 = 0.1042.

An Efficient One-step Methyl Esterification of Carboxylic Acid and Deacetylation of Alcohol under BF_3·OEt_2-MeOH

An efficient one-step methyl esterification of carboxylic acid and deacetylation of alcohol under BF3O·Et2-MeOH was developed.

Syntheses,Crystal Structures,and Magnetic Properties of Two Manganese(Ⅱ) Coordination Polymers Based on Bifunctional Pyridine-benzene Carboxylic Acids

Two manganese（II） coordination polymers, namely, {[Mn（PIP）（BIBP）]·（BIBP）0.5}n（1） and {[Mn（PTA）（BIMBP）（H2O）]·H2O（0.69）}n（2）（H2PIP = 5-（4-pyridyl）-isophthalic acid, H2 PTA =6-（4-pyridyl）-terephthalic acid, BIBP = 4,4？-bis（imidazol-1-yl）biphenyl, and BIMBP =4,4？-bis（imidazol-1-ylmethyl）biphenyl）, have been synthesized by using the bifunctional pyrinde-benzene carboxylic acids and bis（imidazole） linkers as mixed ligands to react with Mn SO4,and further characterized by elemental analysis, IR, and PXRD. Compound 1 is in the triclicnic system, space group P1 with a = 10.1089（8）, b = 13.1927（12）, c = 14.0638（12）A, α = 69.437（2）, β= 73.2890（10）, γ = 78.5320（10）o, V = 1671.9（2） A^3, Z = 2, Dc = 1.449 g/cm^3, F（000） = 705,μ（MoK α） = 0.453 mm^-1, S = 1.053, R = 0.0491 and wR = 0.1367 for 5837 unique reflections（Rint =0.0208） with I 〉 2σ（I）. Compound 2 belongs to the monoclicnic system, space group C2/c with a =15.199（3）, b = 19.731（3）, c = 21.537（5） ？, β = 105.228（3）o, V = 6232（2） A^3, Z = 8, Dc = 1.363g/cm^3, F（000） = 2648, μ（MoK α） = 0.475 mm^-1, S = 1.048, R = 0.0489 and wR = 0.1151 for 7414 unique reflections（Rint = 0.0425） with I 〉 2σ（I）. Structural analyses reveal that complex 1 is a4-connected（44.62）-sql bilayer structure with binuclear [Mn2（COO）2] SBU, while complex 2 is a normally（3,5）-connected（42.67.8）（42.6）-3,5L2 monolayer. And the sheets interacted with the adjacent sheets through weak interactions, finally giving a stable three-dimensional（3D）supramolecule. Besides, the variable-temperature magnetic susceptibility measurement of complex1 was investigated.

Efficient Debromination of Vicinal a, b-Dibromo Carboxylic Acid Derivatives with the Sm/HOAc System

The ? ?vicinal dibromo carboxylic acid and its derivatives were debrominated with Sm/HOAc system to afford the corresponding cinnamic acid and its derivatives in good yields under mild conditions.

A Novel Three-dimensional Mn(Ⅱ) Coordination Polymer Constructed from Biphenyl-3,3',5,5'-tetracarboxylic Acid and Water

The title Mn（Ⅱ） coordination polymer,poly{[heptaaqua-（μ4-bi-phenyl-3,3？,5,5？-tetracarboxylate）-bimanganese（Ⅱ）] pentahydrate},[Mn_2（bpta）（H_2O）_7]_n·5n H_2O（I）,is crystallized from a mixture of biphenyl-3,3？,5,5？-tetracarboxylic acid（H_4bpta） and MnCl_2·4H_2O in waterethanol under room temperature. Its asymmetric unit consists of one and two halves of crystallographically independent Mn（Ⅱ） cations,one fully deprotonated H4 bpta ligand,seven coordinated water molecules and five solvent water as guest molecules. In I,each Mn（Ⅱ） atom is octahedrally coordinated by six oxygen atoms from bpta^（4-） anions and coordinated water molecules. In the Mn（Ⅱ） cations,one half Mn（Ⅱ） ion of them located at a 2-fold axis generating a trinuclear [Mn_3（H_2O）_2（RCOO）_2] linker by μ1,1-O（water） and μ1,3-O,O？（carboxylate） bridges and another half Mn（Ⅱ） ion with an inversion is a mononuclear linker. These neighbouring trinuclear and mononuclear Mn（Ⅱ） cations are linked together by biphenyl-3,3？,5,5？-tetracarboxylates to form a three-dimensional framework with a（42.84） topology of a（4,4）-connected net,in which the positions of the trinuclear [Mn_3（H_2O）_2（R-COO）_2] linker as a 4-connector linking four bpta^（4-） ligands in I reproduce an eagle-shaped arrangement. The polymeric structure exhibits a water channel with an accessible void of 797.1 ？~3,amounting to 15.7% of the total unit-cell volume. Each of the cavities in the network is occupied by solvent water molecules.