【作者】 孙慧；

【导师】 韦奇；

【作者基本信息】 北京工业大学 ， 材料学， 2009， 硕士

【摘要】 主-客体复合介孔材料在催化、传感、吸附、光学和电致发光等领域存在潜在的应用前景。本论文,采用SnCl₂·2H₂O作为锡源,通过浸渍法和水热合成法分别制备出锡物种组装的SnO₂/MPS和Sn-PMOs介孔材料。采用XRD、TEM、N2吸附-脱附、UV-Vis、XPS、红外光谱等表征手段对材料的结构进行分析,并初步探讨了主-客体复合材料作为催化剂在苯酚羟基化方面的应用。XRD、EDS和FT-IR证明采用浸渍法客体SnO₂能成功组装在主体MPS孔道中;同时在合成过程中,溶剂介质的不同影响SnO₂/MPS的介观有序度:采用乙醇为溶剂介质时,主体MPS保持良好的六方有序结构,而当溶剂介质为水时,主体MPS在介观尺寸上为无序结构。由于客体SnO₂占据了主体孔道空间,造成主-客体复合材料SnO₂/MPS的孔容、孔径和比表面积减少。在水热合成-焙烧制备SnO₂/MPS介孔复合材料体系中,通过调节nSi/nSn（硅锡摩尔比）研究孔道内组装客体纳米SnO₂的状态以及对主体孔道结构的影响。当nSi/nSn=100时,多数锡取代骨架Si以四配位状态存在于MPS网络骨架中;当nSi/nSn减小至50时,六配位Sn发生聚集形成晶态SnO₂分布在介孔材料孔道中,此时,MPS依旧保持良好的介观有序性和孔结构;当nSi/nSn=10时,更多的纳米晶态SnO₂分布在介孔材料孔道中,但MPS的孔道结构遭到一定程度的破坏。在水热合成-萃取制备Sn-PMOs介孔复合材料体系中,合成过程并没有造成主体骨架中的有机基团-CH₂-CH₂-的断裂。当nSi/nSn=100和50时,多数锡取代骨架Si以四配位状态存在于PMOs的网络骨架中。随着锡含量的增加,当nSi/nSn=20时,一部分六配位Sn发生聚集形成纳米晶态SnO₂分布在主体孔道中,造成主体介孔材料的介观有序度、孔容、孔径和比表面积的降低。将主-客体复合材料作为催化剂应用于苯酚羟基化反应,结果表明,样品的催化性能与客体锡物种的量以及锡物种的存在状态有密切关系。其中样品Sn-PMOs-50表现出的催化活性最好,其苯酚选择率高达39.2%,邻苯二酚的选择率为46.3%,对苯二酚的选择率为24.8%。更多还原

【Abstract】 Metal incorporated mesoporous materials have a large number of potential applications in catalysis, sensing, adsorption, photonics and electroluminescence. In the present thesis, tin was incorporated into mesoporous silica（MPS） and periodic mesoporous organosilica（PMOs） via an impregnation and direct hydrothermal systhesis method using SnCl₂·2H₂O as tin source, respectively, and the structure of the final materials denoted as SnO₂/MPS or Sn-PMOs and their catalysis in the hydroxylation of phenol were also investigated by mesns of XRD, TEM, N2 adsorption-desorption, UV-Vis, XPS and FT-IR measurements.The results of XRD, EDS and FT-IR show that SnO₂ has been successfully confined in the pore channels of MPS by the impregnation method. The mesoscopic ordering of SnO₂/MPS depends on the solvent used during the systhesis: samples synthesized in ethanol retain an intact hexagonal symmetry while water as solvent leads to an amorphous structure. The presence of SnO₂ within MPS causes a drecease of pore volume, pore size and surface area due to the occupation of the pore space by SnO₂ species.For the samples SnO₂/MPS synthesized by the hydrothermal-calcined process, the molar ratio of silica to tin species（nSi/nSn） has a considerable effect on the distribution status of tin species within MPS and the pore structure of silica hosts. At a low concentration of tin species （nSi/nSn=100）, a majority of tin is highly dispersed within the framework by replacing a fraction of silicon atoms. As the content of tin species increases to nSi/nSn=50, a fraction of tin transfers into crystalline SnO₂ confined into the pore channels of MPS, and the tin-incorporated silica still preserves a highly ordered mesoscopic structure and a desirable pore structure. More SnO₂ nanoparticles are confined into the pore channels when the tin concentration further increases to nSi/nSn=10, but at the cost of the mesoscopic ordering and the pore structure of silica hosts.The bridged orgnic groups–CH₂-CH₂- within the framework of the samples Sn-PMOs synthesized by hydrothermal-solvent extracted method remain intact and do not cleave under the systhesis conditions. At a low tin concentration in the mixture （nSi/nSn=100 and 50）, tin species are demonstrated to enter the framework as the substitutes of a fraction of silicon atoms. When the tin concentration further increases to nSi/nSn=20, additional crystalline SnO₂ nanoparticles are observed in the pore channels, leading to a significant loss of mesoscopic ordering and a decrease of pore volume, pore size and surface area.The catalysis of Sn-incoporated silica mesoporous materials in the hydroxylation of phenol is closely related to the amount and distribution status of tin species within the silica hosts.The samples Sn-PMOs-50 show the best catalytic activity, with a phenol conversion up to 39.2% and a CAT and HQ selectivity of 46.3% and 24.8%, respectively.更多还原