纳米片层为基元的整体式炭的构筑及其吸附CO2行为研究

Physical adsorption process is an effective approach for the separation of low concentration CO2-containing gases, where the structures and properties of adsorbents are the key issues that influence the separation efficiency. Porous carbons are believed to be one of the most promising candidates for CO2 adsorption and separation. However, due to the poor availability of model carbon-based adsorbents, the adsorption and diffusion mechanism of CO2 on porous carbons are still uncertain. These have become the bottleneck for further development of high-performance adsorbents. Hence, this project aims to develop monolithic carbons based on benzoxazine chemistry through self-assembly strategy in solution. The monoliths have a continuous skeleton consisting of nanosheets, hierarchical porosity (micro-, meso-, macropore), which can be fabricated as monolithic column for CO2 adsorption and separation from different gases. By controlling the connection way of carbon nanosheets, and subsequent microphase separation behavior, the mass diffusion rates of adsorbates should be improved. Then, the introduced mesopores in the carbon nanosheets can act as transportation channels and enhance the internal diffusion rates of adsorbates. Meanwhile, micropores with matchable dynamic size of CO2 molecules will be created on the mesopore walls, which can facilitate the adsorption capacity and selectivity of CO2. Based on various in situ spectroscopy methods, we will clarify the correlations between carbon nanostructures and CO2 adsorption performances, and develop principles about controlled synthesis and functions integration. Consequently, the levels of fundamental researches in CO2 separation and reuse will be potentially strengthened.

物理吸附法是分离低浓度CO2的有效方法，吸附剂的结构和性质是决定吸附效果的关键因素，多孔炭用于吸附分离CO2具有独特的优势。但在动态条件下多孔炭孔隙结构对CO2吸附行为的影响规律尚不清晰，主要是因为现有模型吸附材料存在一定缺陷。本项目提出基于苯并噁嗪化学，以纳米薄片为骨架结构单元，采用溶液化学路线，构建具有多级孔道（微孔-介孔-大孔）的整体式炭质模型吸附材料，并直接封装为吸附柱，研究其对CO2的动态吸附分离性能。控制纳米片层之间的交联结构，经微区相分离形成连续贯通的大孔，提高传质速率；在纳米炭片中引入介孔，建立微孔与大孔的输运通道，强化内扩散速率；在介孔孔壁创制与CO2分子动力学尺寸匹配的微孔，提高吸附容量和选择性。通过精确调变微孔、介孔、大孔的尺寸和比例，阐明孔隙结构对CO2吸附行为的影响规律，借助谱学分析，揭示CO2分子在炭表面的动态吸附特征，为高性能吸附材料的制备提供科学依据。

CO2高效捕集是环境与能源领域的研究热点。物理吸附法吸附速率快、易再生，无设备腐蚀、能耗低，相对绿色、环保。在物理吸附过程中，吸附剂的结构和性质是决定吸附效果(吸附量、选择性、吸附速率等)的关键因素。微孔炭在吸附分离领域表现出良好的吸附选择性，孔径分布都在微孔区域，实际应用过程需要粘结成型，导致吸附剂孔隙堵塞、床层压降大、吸附剂粉化严重等问题。为了理解炭结构与CO2吸附性能之间的构效关系，亟需设计合成一种宏观和微观结构可以精确调控的模型吸附材料。.二维结构的纳米材料在平面法线方向的扩散距离短，应用于气体吸附，可促进传质。该项目以提高吸附剂捕集效率为核心，以纳米片层为结构单元，基于溶液自组装方法，构建了具有多级孔道特征的整体式炭质模型吸附材料，实现了多元组份协同组装化学机制和相分离过程的有效调控；通过纳米铸型法原位合成微孔-中孔-大孔串联的多级孔炭材料，提高了其在CO2吸附分离中的传质特性与吸附选择性，CO2/N2和CO2/CH4混合气体的分离选择性分别为40和18，实现了CO2的高效分离；利用温控相转变过程，制备了孔隙通透的超微孔纳米炭片，炭片厚度在30-65 nm内精确可控，微孔孔径在0.53-0.58 nm范围内精确可调，实现了＜2 nm尺度下，对多孔炭材料微孔的精确控制；采用纳米定制作为指导理念，以氧化石墨烯为结构导向剂，成功制备了微观形貌可控、结构可调的整体式炭分子筛吸附剂，研究材料对甲烷中二氧化碳的吸附分离性能，动态选择性高达80.4，且该整体式炭材料具有良好的机械性能，无需引入粘结剂，可直接填装至吸附柱中进行动态分离测试，为高性能吸附材料的制备提供科学依据。通过精准调控炭材料的多级孔道和表面结构，揭示了多孔炭孔隙结构对CO2吸附行为的影响规律及CO2分子在炭表面的动态吸附特征。为高效吸附剂的设计研发提供了实验和理论指导。