基于二维材料取向调控的杂化膜制备与传质机制研究

Hybrid membranes composed of the polymer and two-dimensional materials have become a research hotspot in the field of membrane separation, which combine the superior membrane-forming properties of the polymer and the regular stacking channels of two-dimensional materials. Inspired by the structure of cell membrane with transmembrane aquaporin, vertical two-dimensional channels in hybrid membranes can shorten the mass transfer path and increase effective mass transfer distance and area to intensify the mass transfer process. Polyvinyl alcohol (PVA) with high stability is selected as the polymer matrix, and expanded graphite nanosheets with regular stacking channels are selected as two-dimensional materials. Magnetic expanded graphite nanosheets (m-EGN) are fabricated by loading Fe3O4 nanoparticles on the surface of EGN to increase the magnetic responsiveness. Vertical two-dimensional channels in the hybrid membranes are achieved by aligning m-EGN using a magnetic field. The physical and chemical microenvironment of the channels in the hybrid membranes is regulated by the structure of m-EGN (including size, hydrophilic functional groups and interlayer distance) and their orientation and content in PVA matrix. The mass transfer properties of m-EGN and PVA are matched and optimized collaboratively. Hopefully, this project could clarify the mechanism of structure regulation and mass transfer intensification from the orientation of two-dimensional materials, acquire pervaporative membranes with high performance for fuel ethanol, and finally provide a new avenue for designing and fabricating polymer-inorganic hybrid membranes.

高分子-二维材料杂化膜综合了高分子良好的成膜性和二维材料规整堆积孔道，成为分离膜领域的研究热点。受细胞膜水通道蛋白跨膜结构启发，在杂化膜内构筑垂直取向的二维孔道，可缩短分子传质路径、增大有效传质距离和传质面积，达到强化传质目的。本项目选用高稳定性聚乙烯醇（PVA）为高分子，选用具有规整堆积孔道的膨胀石墨纳米片为二维材料，在其表面负载Fe3O4纳米颗粒制备具有高磁响应性的磁性膨胀石墨纳米片（m-EGN）。利用外磁场实现杂化膜内m-EGN垂直取向，构筑具有垂直二维孔道的杂化膜。通过m-EGN结构（尺寸、亲水基团和片层间距）及其在PVA内的取向和含量调控杂化膜内传质通道的物理化学微环境，实现m-EGN与PVA传质性质的匹配与协同优化。通过本项目开展，阐明二维材料取向调控杂化膜结构和强化传质机制，制备出高性能燃料乙醇脱水渗透蒸发膜，为杂化膜的设计和制备提供新思路。

分子选择型渗透蒸发分离膜的可控制备与高效传质是膜和膜过程领域的前沿。本项目面向国家对清洁能源和水资源短缺等能源和环境问题的重大战略需求，围绕二维材料在铸膜液中的取向调控和杂化膜内高分子与无机材料传质性质的匹配与协同优化两个共性关键科学问题，沿着“材料-方法-结构-微环境-机制-性能”全链条思路，系统地开展分子选择型渗透蒸发分离膜设计制备和高效过程的研究。突出成果如下：.（1）通过磁场诱导，调控二维纳米片在膜中的取向分布，构建垂直取向的二维孔道，缩短分子传质路径，增大有效传质距离和传质面积，强化传质过程。.（2）将自阵列法引入杂化膜的制备。基于“进化-选择”生长机制，二维水滑石在生长过程中自发在基底上形成垂直取向的阵列，构建垂直传质通道，强化传质过程。.（3）采用混合维度组装策略，将二维COF纳米片与一维纤维素纳米纤维或COF纳米带进行组装，促进COF膜孔径的有效调控并提高其机械强度。实现对COF孔道结构的高效利用,有助于克服膜渗透性与选择性的trade-off制约。.（4）从膜表面和层间通道两方面对氧化石墨烯（GO）膜进行改性，制备高性能的GO膜。通过提高膜表面亲水性，增强层间相互作用，优化膜内层间通道物理化学微环境，实现对膜结构的精密构筑，强化分离过程。.通过项目开展，建立了膜分离过程高效强化的新途径，获得了多种突破渗透性-选择性trade-off效应、超越upper-bound上限的高性能分子选择型分离膜。在Nature Sustainability、Nature Communications、Angewandte Chemie、Nano Letters 、Journal of Materials Chemistry A、Journal of Membrane Science等高水平期刊发表论文共28篇。申请发明专利5项，获授权发明专利2项，培养博士生3名，硕士生14名。本项目在规整传质通道精密构筑与物理化学微环境调控、突破膜trade-off效应制约、制备高性能的分子选择型分离膜等方面取得了显著进展，为发展高性能膜材料与高效膜过程奠定了理论与技术基础。