【作者】 王娟；

【导师】 鲁统部；

【作者基本信息】 天津理工大学 ， 凝聚态物理， 2019， 硕士

【摘要】 在催化剂和可见光的作用下,将醇类分子选择性氧化为目标化合物和氢气具有广阔的应用前景。目前已报道的光催化醇氧化体系存在以下问题:（1）光催化剂在水溶液中的反应活性及对醇类氧化产物的选择性不高;（2）光催化剂的稳定性较差,且需要贵金属/非贵金属助催化剂的参与。由于β-环糊精（β-CD）和疏水底物之间存在主客体相互作用,基于此,我们将β-CD修饰到硫化镉纳米晶表面,构筑了环糊精修饰的硫化镉纳米晶（CdS-CD）复合体系,并成功地将其应用于水溶液中可见光驱动醇分子的选择性转化的研究。利用β-CD对醇分子的主客体相互作用,使醇分子在硫化镉纳米晶表面富集,从而提高了醇分子的催化氧化效率和选择性。主要研究内容如下:1、将β-巯基环糊精（SH-β-CD）和油酸包裹的硫化镉纳米晶（CdS-OA）进行配体交换反应,构建了CdS-CD,并探讨了其与醇分子之间的主客体键合行为。通过核磁共振氢谱证明环糊精与底物苯甲醇、1-苯基乙醇分子之间具有非共价主客体键合作用;利用Job曲线和紫外滴定实验探究环糊精与底物的键合比及键合常数。实验结果显示:环糊精与苯甲醇、1-苯基乙醇的键合比均为1:1,键合常数分别是146 M^-1和160 M^-1。2、研究了CdS-CD在可见光驱动醇类化合物催化转化方面的应用。通过调节醇类化合物的浓度,CdS-CD可以将不同的醇分子高选择性地转化成邻二醇/醛酮化合物及氢气。具体内容如下:（1）利用浓度梯度实验筛选出苯甲醇氧化为二聚体的最佳浓度是0.3M,氧化为苯甲醛的最佳浓度是0.001 M;（2）在醇浓度为0.3 M的条件下,研究了CdS-CD对不同醇类化合物催化转化为邻二醇的催化活性,结果表明,CdS-CD对苯甲醇、1-苯基乙醇、2-甲基苯甲醇、3-甲基苯甲醇、4-甲基苯甲醇、2-呋喃甲醇、2-噻吩甲醇、3-羟甲基吡啶、4-氯苯甲醇均表现出较高的催化活性和选择性;（3）在醇浓度为0.001 M的条件下,研究了CdS-CD对不同醇类化合物催化转化为醛酮的催化活性,结果表明,CdS-CD对苯甲醇、1-苯基乙醇、2-甲基苯甲醇、3-甲基苯甲醇、4-甲基苯甲醇、2-噻吩甲醇、2-呋喃甲醇均表现出较高的转化率和选择性。实验结果表明:将环糊精修饰到纳米晶表面不仅可以提高CdS纳米晶在水中的稳定性,而且可以显著提高CdS纳米晶对醇类化合物转化的选择性和活性。3、通过动力学同位素效应实验（KIE）、电子顺磁共振波谱测试（EPR）和客体竞争实验证明上述反应为主客体作用促进的光催化自由基反应,并对光催化反应机理做出了合理推测。更多还原

【Abstract】 Selective conversion of alcohols into corresponding target products and hydrogen under the action of catalyst and visible light has wide application prospects.The reported photocatalytic alcohol oxidation systems have the following disadvantages:（1）poor reaction activity and selectivity of photocatalyst in aqueous medium;（2）unsatisfied stability of the photocatalyst and the additional participation of noble/non-noble metals to act as a co-catalyst.Benefitting from the host-guest interactions betweenβ-cyclodextrin（β-CD）and hydrophobic substrates,we modifiedβ-CD to the surface of CdS nanocrystals to construct a cyclodextrin-modified CdS nanocrystals composite system（CdS-CD）,which was subsequently employed to the selective conversion of alcohols under visible-light irradiation in water.The host-guest interaction betweenβ-CD and alcohols can enrich them on the surface of CdS nanocrystal,thereby improving the catalytic oxidation efficiency and selectivity.The main research details include the following parts:1、Theβ-mercaptocyclodextrin（SH-β-CD）and oleic acid capped CdS nanocrystals（CdS-OA）were used to construct CdS-CD through ligands exchange reaction and the host-guest interactions betweenβ-CD and alcohol molecules were explored.The binding interactions betweenβ-CD and model substrates（benzyl alcohol and 1-phenylethanol）were investigated by ¹H NMR experiments.The bonding ratio and binding constants betweenβ-CD and model substrates were investigated by Job plot and UV titration experiments.The results show that both of the bonding ratio were 1:1,and the corresponding binding constants were146 M^-11 and 160 M^-1.2、The application of CdS-CD in the selective conversion of alcohols under visible light driven were studied.Just through changing the concentration of the alcohols,CdS-CD can convert different alcohol molecules into vicinal diols/aldehyde ketone compounds and hydrogen with high selectivity.The specific contents are as follows:（1）Optimize the substrate concentration of alcohols by concentration gradient experiment.The results show that the optimum concentrations for the products of vicinal diols and benzaldehyde are 0.3 M and 0.001 M,respectively;（2）Under the condition of alcohol concentration of 0.3 M,the catalytic activity of CdS-CD for the catalytic conversion of different alcohols to vicinal diols was studied.The results indicate that CdS-CD possesses high catalytic activity and selectivity for benzyl alcohol,1-phenylethanol,2-methylbenzyl alcohol,3-methylbenzyl alcohol,4-methylbenzyl alcohol,2-furan methanol,2-thiophene methanol,3-pyridinemethanol and4-chlorobenzyl alcohol;（3）The catalytic activity of CdS-CD for catalytic conversion of different alcohols to aldehydes or ketones was studied under the condition of alcohol concentration of 0.001 M.The results showed that CdS-CD exhibited high conversion and selectivity for benzyl alcohol,1-phenylethanol,2-methylbenzyl alcohol,3-methylbenzyl alcohol,4-methylbenzyl alcohol,2-thiophene methanol,and 2-furan methanol.These results indicate that the modification of cyclodextrin to the surface of CdS nanocrystals can not only improve the stability of CdS nanocrystals in water,but also significantly improve the selectivity and activity of CdS nanocrystals for the conversion of alcohols.3、The kinetic isotope experiment（KIE）,electron paramagnetic resonance spectroscopy（EPR）and guest competition experiments were conducted to clarify and propose the possible reaction mechanism,which was a free radical reaction process promoted by the host-guest interactions.更多还原