N、F共掺杂TiO2可见光响应光催化剂的酸催化水解法制备及表征

采用酸催化水解法由TiCl4、NH4F混合液合成N、F共掺杂可见光响应TiO2光催化剂(TONF).以苯酚为模型物,考察了催化剂在可见光区、紫外光区的催化活性.采用X射线光电子能谱(XPS)、紫外.可见漫反射光谱(DRS)、X射线衍射(XRD)、打描电子显微镜(SEM)及低温氮物理吸附对光催化剂的晶相结构、光谱特征和表面结构等进行表征.结果表明,适量的N、F共掺杂TONF催化剂表现出较高的可见光催化活性.N、F共掺杂可显著提高TiO2分散性能,促进锐钛矿相的形成,抑制其向金红石相转变,提高相转变温度.N掺杂可提高TiO2在可见光区的吸收;F掺杂可使TiO2能隙变窄.     

N、F共掺杂TiO2可见光响应光催化剂的酸催化水解法制备及表征

采用酸催化水解法由TiCl4、NH4F混合液合成N、F共掺杂可见光响应TiO2光催化剂(TONF). 以苯酚为模型物, 考察了催化剂在可见光区、紫外光区的催化活性. 采用X射线光电子能谱(XPS)、紫外-可见漫反射光谱(DRS)、X射线衍射(XRD)、扫描电子显微镜(SEM)及低温氮物理吸附对光催化剂的晶相结构、光谱特征和表面结构等进行表征. 结果表明, 适量的N、F共掺杂TONF催化剂表现出较高的可见光催化活性. N、F共掺杂可显著提高TiO2分散性能, 促进锐钛矿相的形成, 抑制其向金红石相转变, 提高相转变温度. N掺杂可提高TiO2在可见光区的吸收; F掺杂可使TiO2能隙变窄.     

N、F共掺杂可见光响应介孔TiO2光催化剂:纤维素模板剂合成及活性

以纤维素为模板剂,TiCl4为钛源,采用液相水解-沉淀法制备了浅黄色的N、F共掺杂可见光响应介孔TiO2催化剂(TiONF)。以苯酚为模型物,考察了TiONF在紫外光区、可见光区及太阳光下催化活性;采用X射线光电子能谱(XPS)、傅里叶变换红外(FTIR)、紫外-可见漫反射光谱(UV-Vis DRS)、X射线衍射(XRD)、热重/量热扫描(TG/DSC)、透射电镜(TEM)及低温N2物理吸附-脱附等技术对TiONF催化剂的结构进行了表征。结果表明,以纤维素为模板剂合成适量N、F共掺杂的TiONF催化剂在紫外光区、可见光区及太阳光下均表现出较高的活性,且高于无模板剂合成的TiONF催化剂的活性。N、F共掺杂提高了TiO2表面羟基数量和锐钛矿相TiO2向金红石相转变的温度;N掺杂形成新的能级结构,诱发TiO2可见光催化活性;F掺杂促进TiO2粒子表面氧空穴产生,致使TiO2粒子表面酸度和Ti3+增加。另外,纤维素的加入可减小TiONF颗粒平均尺寸,改善催化剂分散性,提高催化剂比表面积。     

SiO2负载氮掺杂TiO2可见光响应光催化剂的制备及性能

以四氯化钛为钛源,尿素为氮源,采用液相水解-沉淀法制得SiO2负载N掺杂TiO2可见光响应TiO2-xNy/SiO2光催化剂(TSN)。以苯酚为模型物,考察了TSN在可见光区、紫外光区及太阳光下的光催化活性,以及催化剂的使用寿命、分离性能。采用XPS、FTIR、UV-Vis DRS、XRD、TEM和低温氮物理吸附等对催化剂的结构进行表征。结果表明,N以阴离子形式进入TiO2体相并置换晶格中的O,适量N掺杂的TSN在紫外光区、可见光区及太阳光下均表现出较高的活性。SiO2与TiO2界面间有Ti-O-Si键形成,结合牢固。N掺杂在TiO2表面生成Ti-O-N键,形成新的能级结构,使催化剂的吸收红移至450~500 nm,诱发TiO2可见光催化活性。SiO2负载可减小TiO2颗粒平均尺寸,增加催化剂比表面积;同时SiO2负载还可改善催化剂的分离性能,提高催化剂使用寿命。     

离子液体-水混合介质中合成N、F共掺杂宽光域响应多孔TiO2光催化剂及性能

以TiCl4为钛源,离子液体-水为混合溶剂,采用液相水解-沉淀法制得浅黄色的N、F共掺杂宽光域响应多孔TiO2光催化剂(TiONF).以苯酚为模型物,考察了TiONF在紫外光区、可见光区及太阳光下催化活性.采用X射线光电子能谱(XPS)、紫外-可见漫反射光谱(DRS)、透射电镜(TEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱及低温N2吸附-脱附等技术对TiONF的结构进行表征.结果表明,在离子液体-水混合介质中合成适量N、F共掺杂的TiO2在紫外光区、可见光区及太阳光下均表现出较高的活性,且高于纯水介质中合成TiONF的活性.离子液体-水混合介质有利于N、F进入TiO2晶格中;N、F共掺杂后在TiO2表面生成Ti―O―N键,形成新的能级结构,使催化剂的吸收红移至450-530nm,诱发TiO2可见光催化活性;同时,N、F共掺杂提高了TiO2表面羟基数量;还提高了TiO2相转变温度,减缓了相转变速率.另外,在离子液体-水混合介质中合成的TiONF较纯水介质中合成的TiONF粒子小、分散性好、比表面积大.     

S掺杂宽光域响应Ti1-xSyO2光催化剂的制备及表征

以TiCl4和硫脲为主要原料, 采用酸催化水解法制得浅黄色S掺杂Ti1-xSyO2光催化剂. 以苯酚为模型物, 考察了Ti1-xSyO2在可见光区、紫外光区及太阳光下的催化活性. 采用XPS、DRS、XRD、FT-IR、SEM、低温氮物理吸附对光催化剂进行表征. 结果表明, 掺杂S以S6+形式置换TiO2晶格中的Ti4+, 适量S 掺杂的Ti1-xSyO2在可见光区、紫外光区及太阳光下均表现出较高的光催化活性.掺杂S 在TiO2表面形成新的能级结构, 使催化剂吸收红移至450-550 nm, 诱发可见光催化活性;紫外光照射下, 新形成的能级结构与体相TiO2形成复合半导体结构, 捕获光生空穴, 提高光生电子鄄空穴分离效率.同时, S掺杂可以改善TiO2的分散性, 增加其比表面积SBET并提高相转变温度.     

N掺杂对TiO2形态结构及光催化活性的影响

以TiCl₄为钛源,采用酸催化水解法合成TiO₂前驱体,在NH₃/N₂气氛下经不同温度处理制得浅黄色的N掺杂TiO₂(TON)光催化剂。以苯酚为模型物,考察了催化剂在紫外光区、可见光区及太阳下催化活性;采用DRS、XPS、XRD、FTIR、SEM及低温氮物理吸附对光催化剂的晶相结构、光谱特征和表面结构等进行表征。系统研究了N掺杂对TiO₂形态结构及光催化活性的影响。结果表明,掺杂N以阴离子形式进入TiO₂体相中置换晶格中的O,适宜温度下制得适量N掺杂的TON在紫外光区、可见光区及太阳光下均表现出较高的活性。N掺杂在TiO₂表面生成Ti-O-N键,形成新的能级结构,使催化剂的吸收红移至450～550 nm,诱发TiO₂可见光催化活性。同时高温下煅烧,N掺杂可抑制TiO₂晶粒生长,减缓TiO₂粒子间团聚,提高锐钛矿相向金红石相转变温度,减缓相转化速度。     

S掺杂S-TiO_2/SiO_2可见光响应光催化剂的制备及性能

以四氯化钛为钛源,硫脲为硫源,采用液相水解-沉淀法制备了S掺杂的TiO2/SiO2(S-TiO2/SiO2)催化剂,并以苯酚为模型物,考察了催化剂在可见光区、紫外光区和太阳光下的光催化活性,以及催化剂的使用寿命和分离性能.采用X射线光电子能谱、傅里叶变换红外光谱、紫外-可见漫反射光谱、X射线衍射、透射电镜及N2吸附-脱附等技术对催化剂进行了表征.结果表明,S以+6价形式进入TiO2体相并置换晶格中的Ti4+,适量S掺杂的S-TiO2/SiO2在紫外光区、可见光区和太阳光下均表现出较高的光催化活性.SiO2与TiO2界面间有Ti-O-Si键形成,结合牢固.S掺杂在TiO2表面生成Ti-O-S键,形成新的能级结构,使光催化剂在450～550nm产生吸收,诱发TiO2可见光催化活性;同时提高了TiO2表面羟基数量.SiO2的加入可减小TiO2颗粒的平均尺寸,增大催化剂的比表面积,改善催化剂的分离性能,提高催化剂的使用寿命.     

硼硫共掺杂TiO2的光催化性能及掺杂机理

采用水热法制备了硼硫共掺杂的TiO2光催化剂(TiO2-B-S),并用其光催化降解甲基橙.结果表明,在240℃下水热反应12h时制得的TiO2-B-S具有较高的催化活性,紫外光照射50min和太阳光照射230min时对甲基橙的降解率分别达99.8%和81%.X射线粉末衍射、紫外-可见漫反射光谱和X射线光电子能谱等研究表明,TiO2-B-S为锐钛矿晶型,硫硼掺杂能抑制TiO2粒径的生长;TiO2-B-S同时具有较高的紫外光和可见光活性的原因可能是掺杂的硼以B3 进入晶格中,导致TiO2晶格畸变,带隙变窄.掺杂的硼和硫还提高了TiO2的表面酸度和对可见光的吸收.     

N掺杂富含(001)晶面TiO_2纳米片的制备及N掺杂浓度对可见光催化活性的影响(英文)

采用水热法制备了富含(001)晶面的锐钛矿型TiO2纳米片,并通过改变热处理过程中NH3流速制备不同N掺杂浓度的TiO2纳米片.运用X射线衍射、场发射扫描电镜、高分辨率透射电子显微镜、紫外-可见漫反射光谱、X射线光电子能谱和荧光光谱对光催化剂进行了结构和性能表征,并以罗丹明B为目标降解物,考察了N掺杂浓度对TiO2纳米片可见光催化活性的影响.结果表明,NH3流速为40ml/min时制备的N掺杂TiO2纳米片具有最低的光生电子-空穴复合速率,最高的OH产生能力并表现出最高的光催化活性.同时,讨论了N掺杂浓度对TiO纳米片可见光催化活性影响的机理.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.