Solid Bronsted acidity boosts adsorption reactivity of nano-adsorbent for water decontamination

Despite the development of various Lewis acidic nano-adsorbents for fluoride removal through innersphere coordination,strong competition for hydroxyl ions still hinders efficient water defluoridation.In addition,the critical issue of polysilicate scaling that results from the ubiquitous silicates must be addressed.To tackle these issues,an alternative approach to enhancing adsorption reactivity by modifying nano-adsorbents with dual Lewis and Bronsted acidity is proposed.The feasibility of this approach is demonstrated by growing zirconium phosphate(ZrP)inside a gel-type anion exchanger,N201,to produce nanocomposite ZrP@N201,in which the confined ZrP contained an otherwise metastable amorphous phase with Lewis acidic Zr^(4+) sites and Bronsted acidic monohydrogen phosphate groups(-O_(3)POH).Compared with the Lewis acidic nano-zirconium oxide analog(HZ0@N201),ZrP@N201 exhibited a greatly improved adsorption capacity(117.9 vs.52.3 mg/g-Zr)and mass transfer rate(3.56×10^(-6) vs.4.55×10^(-7) cm/s),while bulk ZrP produced a thermodynamically stableα-phase with Bronsted acidity that exhibited negligible adsorption capability toward fluoride.The enhanced defluoridation activity of ZrP@N201 is attributed to Bronsted acidity and the increased outer electron density of ZA+sites,as corroborated using XPS and solid-state NMR analysis.Moreover,Bronsted acidity strengthens the resistance of ZrP@N201 to silicate,allowing its full regeneration during cyclic defluoridation.Column tests demonstrated 3-10 times the amount of clean water from(waste)for ZrP@N201 as compared to both HZO@N201 and the widely used activated aluminum oxide.This study highlights the potential of developing nano-adsorbents with dual acidities for various environmental remediation applications.

Application of Bronsted acid ionic liquids as green catalyst in the synthesis of 2-propanol with reactive distillation

Five Br?nsted acidic ionic liquids(ILs) were prepared and characterized by FT-IR,~1H NMR and ^(13)C NMR. Their catalytic activities for the synthesis of 2-propanol(IPOH) via transesterification of isopropyl acetate(IPAc) with methanol(Me OH) were investigated. Among all the tested ILs, [Ps-mim]HSO_4 performed best and was used as catalyst for further studies. The reaction kinetics were carried out to correlate the parameters in a homogeneous second order kinetic model. It has been found that there is close agreement between the calculated and experimental values. The high-pressure batch reactive distillation experimental apparatus was set up in order to enhance the conversion of IPAc. A high conversion of IPAc of 99.4% was obtained under the optimal reaction conditions. The catalyst [Ps-mim]HSO_4 can be recycled easily by a rotary evaporator and reused without any further treatment. The catalyst had been repeatedly used for four times and no obvious changes in the structure of catalyst could be observed.

Facile Aldol Reaction Between Unmodified Aldehydes and Ketones in Bronsted Acid Ionic Liquids

A series of condensation reactions of unmodified ketones and aromatic aldehydes to prepare α,β-unsaturated carbonyl compounds by means of Aldol reactions in Bronsted acid ionic liquids（BAILs）was explored.1-Butyl-3-methylimidazolium hydrogen sulphate（BMImHSO4）acting as an effective media and catalyst in aldol reactions was compared with other BAILs,with the advantages of high conversion and selectivity.The product was easily isolated and the left ionic liquid can be readily recovered and reused at least 3 times with almost the same efficiency.The scope and limitation of the present method were explored and the possible catalytic mechanism was speculated.

Low Environmental Load Process for the Beckmann Rearrangement of Cycloalkanone Oximes by Bronsted Acid Catalyst with Cobalt Salts

Beckmann rearrangements of oximes to lactams often require harsh conditions and/or the use of large amounts of acid catalyst. To reduce the amount of Bronsted acid required, and to avoid the formation of a large amount of undesirable byproducts under mild reaction conditions, a low environmental load process was developed. Beckmann rearrangements of cyclohexanone oxime and cyclooctanone oxime were achieved using a combination of a Bronsted acid and cobalt tetra-fluoroborate hexahydrate. Various Bronsted acid catalysts (10 - 20 mol%) were used to obtain the corresponding lactams in high yields at 80℃.

Catalysis performance comparison of a Br?nsted acid H_2SO_4 and a Lewis acid Al_2(SO_4)_3 in methyl levulinate production from biomass carbohydrates

An experimental investigation was conducted to understand the roles of the Br？nsted acid H2SO4 and Lewis acid Al2（SO4）3 in methyl levulinate（ML） production from biomass carbohydrates, including glucose,fructose and cellulose. The product distributions with different catalysts revealed that the Lewis acid was responsible for the isomerization of methyl glucoside（MG）, producing a significant amount of the subsequent product 5-methoxymethylfurfural（MMF）, while the Br？nsted acid facilitated the production of ML from MMF. Al2（SO4）3 was efficient for monosaccharide conversion but not for cellulose. Using ball-milled cellulose with Al2（SO4）3 resulted in a desired ML yield within a reasonable reaction time. The significant catalysis performances of two types of acids will guide the design of efficient catalytic processes for the selective conversion of biomass into levulinate esters.

Preparation of ZSM-5 containing vanadium and Br?nsted acid sites with high promoting of styrene oxidation using 30% H_2O_2

Design and synthesis of low cost and efficacious industrial catalyst for the oxidation of styrene has been an important research project.Herein,ZSM-5 zeolite containing tetrahedral vanadium(V)and Br?nsted acid sites(V-H-ZSM-5)was prepared,and identified by characterizations such as XRD,SEM,UV–vis,NH3-TPD,H2-TPR N2-adsorption/desorption and FTIR.V-H-ZSM-5 performed extremely enhanced catalytic activity for the oxidation of styrene with 30%H2O2 at 40°C.Moreover,in-situ FTIR spectrum was used to investigate the catalytic mechanism.The results demonstrate that Br?nsted acid site could not only increase the adsorption concentration of styrene in the micropores of V-H-ZSM-5 via theπcomplex interaction between double bond of styrene and Br?nsted acid sites,but also increase the oxidation potential of H2O2.The synergetic action of tetrahedral vanadium(V)and Br?nsted acid enhanced the catalytic activity for the oxidation of styrene with 30%H2O2.Impressively,V-H-ZSM-5 performed high reusability within five runs at a low reaction temperature(40°C)for the first time.

BrФnsted Acidic Ionic Liquids: Novel Efficient, Cost-effective and Reusable Solvent-catalysts for Ritter Reaction

Several Bronsted acidic ionic liquids（ILs） were synthesized and used as dual solvent-catalysts for the Ritter reaction of benzonitrile with tert-butanol. In particular, IL11（[NSPTEA][OTF]） showed excellent catalytic activity for the Ritter reaction. In the presence of IL11, various nitriles and tertiary alcohols as well as secondary alcohols were converted smoothly to the corresponding amides in good to excellent yields. In addition, this cost-effective ionic liquid [NSPTEA][OTF] was easily separated from the reaction mixture by extraction with a small amount of water, and was recycled five times without any significant loss in activity.

Oxidative cyclization of allyl compounds and isocyanide: A facile entry to polysubstituted 2-cyanopyrroles

A facile Tf OH-catalyzed oxidative cyclization of allyl compounds and isocyanide has been developed with the assistance of DDQ, where isocyanide is used as the crucial "N" and "CN" sources. Highly functionalized 2-cyanopyrroles are constructed efficiently through a new formal [3 + 2] mode, demonstrating diverse reactivity and synthetic utility in organic chemistry. 2-Cyanopyrrole is converted into a nucleobase analogue of Remdesivir and 5H-pyrrolo[2,1-a]isoindole through a three-step or a two-step sequence, respectively. This protocol features broad substrate scope, operational simplicity and good functional group tolerance.

Design of Ca-type todorokite catalysts with highly active for the selective reduction of NO_(x) by NH_(3) at low temperatures

Ca-type todorokite catalysts were designed and prepared by a simple redox method and applied to the selective reduction of NO_(x) by NH_(3)(NH_(3)-SCR)for the first time.Compared with the Na-type manjiroite prepared by the same method,the todorokite catalysts with different Mn/Ca ratios showed greatly improved catalytic activity for NO_(x) reduction.Among them,Mn8Ca4 catalyst exhibited the best NH_(3)-SCR performance,achieving 90%NO_(x) conversion within temperature range of 70-275℃ and having a high sulphur resistance.Compared to the Na-type manjiroite sample,Ca-type todorokite catalysts possessed an increased size of tunnel,resulting in a larger specific surface area.As increased the amounts of Ca doping,the Na content in Ca-type todorokite catalysts significantly decreased,providing larger amounts of Bronsted acid sites for NH_(3) adsorption to produce NH_(4)^(+).The NH_(4)^(+)species were highly active for reaction with NO+O_(2),playing a determining role in NH_(3)-SCR process at low temperatures.Meanwhile,larger amounts of surface adsorbed oxygen contained over the Ca-doping samples than that over Na-type manjiroite,promoting the oxidation of NO and fast SCR processes.Over the Ca-type todorokite catalysts,furthermore,nitrates produced during the flow of NO+O_(2),were more active for reaction with NH_(3) than that over Na-type manjiroite,benefiting the occurrence of NH_(3)-SCR process.This study provides novel insights into the design of NH_(3)-SCR catalysts with high performance.

Organic Brønsted Acid-Catalyzed Stereoselective Cationic RAFT Polymerization:The Effect of RAFT Agents

The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.

Bronsted acidic ionic liquid [C_3SO_3HDoim]HSO_4 catalyzed one-pot three-component Biginelli-type reaction: An efficient and solvent-free synthesis of pyrimidinone derivatives and its mechanistic study

A series of Bronsted acidic ionic liquids（ILs） were prepared and used for Biginelli-type condensation reaction among aromatic aldehydes, urea or thiourea and cyclopentanone. Through this reaction, the synthesis of various pyrimidinones could be achieved. Of interest, it was found that the reaction was efficiently catalyzed by a novel, eco-friendly functionalized IL [C3SO3HDoim]HSO4, which could be reused for at least 7 times without significantly loss of catalytic activity. The reaction proceeded efficiently at 80℃ to afford the desired products in good yield（up to 96%）. In addition, a possible mechanism that accounted for the IL [C3SO3HDoim]HSO4-catalyzed reaction was proposed.

Synergistic mechanism between Bronsted acid site and active cerium species in hydride transfer reaction over CeY zeolites

In this study,cyclohexene was used as a representative of olefin and catalyzed by CeY zeolites in a fixedbed reactor under mild conditions,and the influence of Ce species in hydride transfer reaction over CeY zeolites was evaluated.CeY zeolites show more excellent hydride transfer properties than HY zeolite.Based on the results of almost identical Bronsted acid properties but not the product distributions for 0.075 CeY and 0.075 CeY(DC)samples,it should be suggested that the Bronsted acid strength and density are not the deciding factors to the hydride transfer reaction.A unique band at 1442 cm^-1 in situ FTIR spectroscopy spectra are assigned to pyridine complexes bonded to a class of active Ce species that could reversibly migrate from the core of SOD cages to its 6-rings mouth towards the supercages.These results provide valuable information that these active Ce species should play a synergistic role with the Bronsted acid sites in enhancing the hydride transfer reaction with a bimolecular mechanism over CeY zeolites.

On Water： Bronsted Acidic Ionic Liquid [（CH2）4SO3HMIM][HSO4] Catalysed Synthesis of Oxindoles Derivatives

Some oxindoles derivatives are synthesized from the condensation of indoles with isatins in the presence of green and recycable catalyst [（CH2）4SO3HMIM] [HSO4] in water at room temperature.

Bronsted Acid Catalyzed gem-Difluoroallylation of Aldehydes and Ketone with β-Tosyloxy-γ,γ-difluroallylboronic Acid Pinacol Ester

A shelf-stable gem-difluorinated reagent β-tosyloxy-γ,γ-difluroallylboronic acid pinacol ester has been prepared, which can be easily used for the preparation of gem-difluorinated homoallylic alcohols through Bronsted acid （PhCO2H） catalyzed gem-difluoroallylation of aldehydes and ketone.

Mechanism of Preparation of Platform Compounds from Lignocellulosic Biomass Liquefaction Catalyzed by Bronsted Acid: A Review

Over the past two decades, research on transforming lignocellulosic biomass into small molecule chemicals byusing catalytic liquefaction has made great progress. Notably, in recent years it has been found the production of smallmolecule chemicals through directional liquefaction of lignocellulosic biomass. Understanding the liquefactionmechanism of lignocellulosic biomass is highly important. In this review, the liquefaction mechanism of lignocellulosicbiomass and model compounds of cellulose are described, and some problems and suggestions to address them aredescribed.

4-(Succinimido)-1-butane sulfonic acid as a Bronsted acid catalyst for synthesis of pyrano[4,3-b]pyran derivatives under solvent-free conditions

4-（Succinimido）-1-butane sulfonic acid as an efficient and reusable Bronsted acid catalyzed the synthesis of pyrano[4,3-b]pyran derivatives under solvent-free conditions.The catalyst can be prepared by mixing succinimide and 1,4-butanesultone that is more simple and safer than the preparation of succinimide sulfonic acid.This method has the advantages of high yield,clean reaction,simple methodology and short reaction time.The catalyst could be recycled without significant loss of activity.

Surface Properties and Etherification in Microemulsion Systems of Novel Bronsted Acid Surfactants

Novel Bronsted acid-surfactants with different alkyl chains were synthesized via a two-step process, and their surface properties were studied. The critical micelle concentration（cmc）, surface tension at the cmc（γcmc）, and ability of these compounds to lower the surface tension by 0.02 N/re（C20 and pC20） were investigated at 25 and 40 ℃. The molecular architecture of the compounds strongly influenced these physicochemical parameters. The ability of these compounds to lower surface tension was found to be good. Etherification in microemulsions formed by these surfactants as well as dodecylbenzenesulfonic acid（DBSA） was performed; surfactants 3a and 3b were found to be much more efficient than dodecylbanzenesulfonic acid（DBSA）.

Imidodiphosphorimidates (IDPis): Catalyst Motifs with Unprecedented Reactivity and Selectivity

The conceptually designed imidodiphosphorimidates(IDPis)have emerged as one of the most potent classes of chiral acid catalysts.They are characterized by enzyme-like,highly confined active site and high acidity,which underlie their wide-reaching applications as Bronsted acid catalysts and as precatalysts for silylium Lewis acids.Many carbon-carbon and carbon-heteroatom bond formation reactions that were deemed intractable could now be attained with spectacular reactivity and selectivity.Substrates that are small,unbiased and/or possess insufficient reactivity such as simple alkenes could now be engaged.The high structural confinement is particularly invaluable to control stereo-and chemoselectivity.The well-defined steric environment offers unique opportunity to control high-energy but structurally unbiased cation intermediates such as the norbonyl cations.Beyond practical appeals such as good scalability as well as ease and modularity of preparation,the extremely low pre-catalyst loadings required to achieve high turnover and stereoselectivity have also come to define a new frontier in organocatalysis.

One-pot remote desymmetrization/Peterson-olefination for the construction of silicon-stereogenic silyl ethers

Chiral silyl ethers and silanols are important synthetic intermediates and bioactive compounds.In this work,we developed a onepot remote desymmetrization/Peterson-olefination of silacyclopentene oxides with benzoic acids in the presence of Martin’s sulfurane.This new methodology not only realizes the atom-economy of Peterson olefination,but also represents a catalytic method for synthesis of silicon-stereogenic silyl ethers.Using a bulky chiral phosphoric acid 4i as organocatalyst,the reactions proceeded efficiently to afford various olefin-functionalized organosilyl ethers in excellent diastereoelectivities(up to 25/1 d.r.)and high enantioselectivities(up to 94%ee).

Iridium-Catalyzed Asymmetric Hydrogenation of Tetrasubstituted Exocyclic Olefins:An Efficient Access to Dexmethylphenidate

An Ir-catalyzed enantioselective hydrogenation of challenging tetrasubstituted exocyclic olefins is disclosed.This new catalytic system tolerates a broad substrate scope and affords valuable chiral cyclic β-amino esters possessing two vicinal stereocenters in high yields and excellent enantioselectivities and diastereoselectivities(up to 94% yield,96% ee,99:1 dr).Control experiments and deuterium-labeling reactions reveal an iminium hydrogenation mechanism upon Brønsted acid-promoted tautomerization of the C=C double bond to cycliciminium intermediates.Density functional theory calculations showcase that the excellent selectivities are derived from C-H…π interaction between the substrate and the chiral ligand.Application in gram-scale preparation of dexmethylphenidate with up to 1500 turnover number is also demonstrated,showing the promising potential of Ir-catalyzed enantioselective hydrogenation in drug synthesis.