介孔分子筛制备、表征及应用

【作者】 盖利刚；

【导师】 王琪珑； 崔得良；

【作者基本信息】 山东大学 ， 无机化学， 2006， 博士

【摘要】 介孔分子筛具有有序的孔道、丰富的表面羟基和形貌。利用介孔分子筛有序孔道为模板，经过前驱物渗透→前驱物转化→脱模制备一维材料，文献中已有很多报道。事实上，由于扩散阻力的影响和分子筛外表面的吸附作用，利用分子筛孔道进行‘纳米浇铸’（nanocasting）制备一维材料，结果往往不令人满意。文献报道，在活性基团（羟基、羰基、羧基、醚键等含氧基团）定向排列的物理模板表面上，通过活性基团和金属离子的配位作用，使金属离子有序排列，可以得到金属纳米线。介孔分子筛具有丰富的表面羟基，以介孔分子筛表面为模板，利用分子筛表面羟基的弱配位能力（亲核性）和表面形貌的多样性，选择合适的反应物和介质，有望在分子筛表面上实现一维材料的控制合成。 我们制备了MCM-41、MCM-48和SBA-15三种硅基介孔分子筛，制备了有机杂化介孔分子筛和金属离子改性介孔分子筛，并对上述分子筛进行了XRD、氮气吸附-脱附、IR、SEM表征。发现在物系中能形成多聚酸根的钒酸盐，在表面活性剂用量较低（CTAB／SiO₂=0.4，molar ratio）的情况下，容易得到有序性较好的V／MCM-48分子筛。 探索了介孔分子筛在无机纳米合成中的应用。用分子筛表面为模板，以GaCl₃作镓源、NaN₃作氮源，苯热法（280-300℃）制备了GaN纳米棒、纳米管、纳米环和纳米晶；以GaCl₃作镓源、Li₃N作氮源，苯热法（260-300℃）制备了GaN纳米线和纳米晶。以GaCl₃作镓源，在受潮分子筛表面上，苯热法（280-300℃）制备了β-Ga₂O₃纳米棒，而β-Ga₂O₃通常在高温下（600℃）才能得到。在GaCl₃、Na₃P和二甲苯反应物系中，以分子筛表面作模板，低温下（70℃）制备了GaP纳米树枝（GaP dendrites）。对上述纳米材料进行了XRD、TEM、HRTEM、EDS、SEM、XPS表征。 发现了分子筛表面羟基的配位-催化作用和分子筛表面形貌的‘助吸附’作用。这两者共同作用，不仅可以提高产物的产率、结晶度，也有助于实现纳米材料的形貌控制合成。对上述不同材质、不同形貌纳米材料在分子筛表面的生长机理，进行了有益的探索。提出了羟基促进→前驱物成膜→薄膜卷曲→成棒的纳米棒生长机理；提出了SLS（solution-liquid-solid）引发的纳米管顶端生长（tip-growth）和基底生长（base-growth）机理；提出了羟基定位-凹面辅助的纳米环生长机理；在更多还原

【Abstract】 It’s known that mesoporous molecular sieves （MMS） are characteristic of orderly channels, plenty of surface hydroxyls and various morphologies. Orderly channels in MMS provide a class of low-cost templates for use in the synthesis of one-dimensional （1D） structures. Generally, this method involves three steps, i.e. infiltration of the pores with an appropriate precursor via a vapor- or solution-based approach, conversion of the precursor to the desired materials, and recovery of the 1D nanostructures by selective removal of the template. In fact, due to the negative effect, originating from diffusive obstruction in the small pores and adsorption function of the exterior surface, it has been difficult to achieve complete filling with high yield of the desired materials. Therefore, much effort is needed to improve the performance of nanocasting in the channels of MMS. It has been reported that metal nanowires can be obtained on the surface of a physical template, on which active functionalities reside in array, e.g. hydroxyls, carbonyls, carboxyls and ethers etc.. These active functionalities coordinate with metal ions, facilitating the formation of metal nanowires. It’s expected that controllable synthesis of 1D structures can be achieved on the surface of MMS, by selecting appropriate reactants and solvent, due to their abundant surface hydroxyls and variable surface morphologies.In this manuscript, three kinds of.Si-based MMS （MCM-41, MCM-48, SBA-15）, organic hybridization MMS and metal ion-containing MMS have been prepared. The synthesized MMS have been characterized by XRD, N₂ adsorption-desorption isotherms, IR and SEM measurements. It has been found that vanadium, which can form polyanions and condense, can form well-orderly V-containing MCM-48 easily, with the molar ratio of 0.4 of CTAB/SiO₂.The applications of MMS in the region of inorganic nano-synthesis have been explored. Nanorods, notubes, nanorings and nanocrystals of GaN have been prepared, respectively, via the reaction of GaCl₃ with NaN₃ at 260-300℃ in benzene solution. Nanofibers and nanocrystals of GaN have been synthesized, respectively, via the reaction of GaCl₃ with Li₃N at 260-300℃ through benzenethermal route. In both of更多还原