介稳相锰氧化物分子筛宏观尺度3D泡沫体结构的软化学可控构筑

Being valuable in many application fields, manganese oxide molecular sieves own excellent properties such as microporosity, semiconductivity, selective sorption, catalytic oxidation with air as the oxygen source, and modification via doping. However, only low-dimensional macroscopic pure-phase structures such as powders, helices and paper-like materials are currently available for manganese oxide molecular sieves, of which these structures are difficult to be handled or separated. This proposal will solve one scientific problem, i.e. to construct macroscopic 3D foam structures with considerable mechanical properties using metastable manganese oxide molecular sieves which are not resistant enough to the high-temperature ceramic foam processes. By utilizing the molecular sieve crystals’ properties of self-assembly that mimics the substrate’s form, a Chimie Douce approach for the construction is proposed herein. Ultra-long nanofibers of the molecular sieves will be prepared with the length much longer than that needed for constructing the macroscopic 2D structure. A foaming agent will be developed to create a free-standing porous foam as a 3D substrate to support the involved molecular sieve fibers to generate a porous foam through the self-assembly that mimics the substrate’s form. This foam of molecular sieve fibers will receive the mechanical properties offered by the self-assembly mechanism. Subsequently, a wet chemistry route of washing with an acidic solution will be applied to remove the solid remains of the foaming agent, whereas the molecular sieve foam will be reserved due to its excellent resistance towards acidic solutions. The macroscopic 3D foam structures of manganese oxide molecular sieves will be thus constructed. The feasibility of this idea is supported by advance research results. Through the studies of this project, the multi-functions of manganese oxide molecular sieves will be carried forward to shine on the platform of macroscopic 3D structures. Therefore, this research is of scientific significance and has application values.

锰氧化物分子筛具有微孔半导体、选择性吸附、空气氧源催化氧化、掺杂改性等优异性质，在多个领域有重要应用价值；但目前仅有粉体、螺旋线、纸张等低维纯相宏观构造，不易操作或分离。本项目重点解决将难耐泡沫陶瓷高温工艺的介稳相锰氧化物分子筛构筑为具有一定机械性能的泡沫体宏观3D构造这一科学问题。利用该分子筛晶体的拟形性自组装功能，提出“软化学构筑路径”：即制备分子筛超长纤维纳米线，长度远超构筑宏观2D构造所需的晶体长度；开发一种发泡膨胀剂，能够形成自支撑的多孔泡沫体形状3D基材，以支撑加入体系中的分子筛纤维通过拟形性自组装生成多孔泡沫体，获得自组装所赋予的机械性能；再于室温湿化学酸洗去除发泡膨胀剂的固相存留物，保留耐酸性强的锰氧化物分子筛，制成该分子筛的泡沫体宏观3D构造。预研结果支持可行性。通过本项目研究，可使锰氧化物分子筛的多项功能在宏观3D构造的平台上得以施展。因此，具有重要科学意义和研究价值。

宏观3D海绵/泡沫体材料在很多领域都具有非常重要的应用。然而，具有良好的物理、机械和电学性能的宏观3D海绵/泡沫体材料的简便制备对于国内外科研人员仍然是一项挑战。本项目采用2种技术路线构筑出宏观3D锰氧化物海绵/泡沫体材料：“基于纳米线的无模板冷冻干燥工艺”和“降低烧结温度的泡沫陶瓷工艺”。并对宏观3D锰氧化物海绵/泡沫体材料的物理、机械和电学性能进行了研究。主要获得以下研究结果：. 1.我们以长径比约为3000的超长OMS-2纳米线为原料通过焙烧温度只有300-400°C的温和的模板路径制备了一系列自支撑的宏观三维MnOx泡沫体材料。煅烧气氛中的O2含量，煅烧温度，煅烧时间对MnOx泡沫体材料的结构，织构，机械性能有显著的影响。其中一些MnOx泡沫体材料具有韧性，其它MnOx泡沫体是脆性材料。. 2.采用基于纳米线的无模板冷冻干燥法制备出了可控密度的宏观三维OMS-2海绵材料。这些三维OMS-2海绵材料具有突出的优点，例如机械性能良好，制备方法简便，电导率较高，高孔隙率，良好的渗透性，良好的催化性能，以及可再生性能。这种OMS-2海绵材料可以从油水混合物中选择性吸附水。OMS-2海绵材料的某些性能随着密度的改变，呈现出系统的增加或者降低的趋势，这揭示了通过调节OMS-2海绵材料的密度来调控OMS-2海绵材料性能的新方法。此外，还采用基于纳米线的无模板冷冻干燥法制备出宏观三维In掺杂OMS-2海绵材料和宏观三维Fe掺杂OMS-2海绵材料，并对其导电性、铁磁性、电催化氧还原等性能进行了研究。. 3.采用简便的一步合成方法成功制备出γ-MnOOH纳米管，通过“层状卷曲机制”解释了γ-MnOOH纳米管的形成机制。基于自组装技术在低温水热条件下成功制备出两种Mn3O4六边形片状微纳多级结构材料。这两种Mn3O4六边形片状微纳多级结构材料是由不同形貌的Mn3O4纳米粒子组装基元自组装而成的。探讨了其形成和生长机制，并研究了其超级电容器电化学性能。这种简便的化学合成路线为可控合成其它的金属氧化物多级结构材料提供了新思路。此外，我们采用无模板冷冻干燥法制备出宏观三维MnOOH泡沫体材料和宏观三维Mn3O4泡沫体材料；并采用简便的方法制备出了宏观二维Mn3O4自支撑纸状材料。Mn3O4原料的自组装功能对宏观二维/三维Mn3O4材料有较大的影响。