促进负载型二氧化碳加氢催化剂高活性位点形成的机制研究

The highly active catalyst is the technical key of high-efficient CO2 hydrogenation, while it is difficult to largely increase the activity of the related supported catalysts. The prevailing preparation methods of the supported catalysts for CO2 hydrogenation, from the viewpoint of catalyst engineering, has to involve high-temperature treatment, simultaneously generating the active species and causing the severe aggregation/crystallization of the active species. As a result, majority of the supported species cannot be upgraded to be highly active sites. To overcome the shortcomings, we plan to separate the process of controllably generating the homogeneous and amorphous supported active species by liquid-phase chemical reduction and that of controllable crystallization of the active species, to directionally promote the fabrication of theoretically high-active sites, with the finite quantity of supported species. With the investigation of different parameters of catalyst preparation impacting on the characters and catalytic activity of the catalysts, the mechanism of the discrete control promoting the fabrication of highly active sites of catalysts is to be elucidated. With the quantum chemistry simulation of the behaviors of CO2 hydrogenation over different catalytic sites, the structure-activity relationship of the active sites, as well as the influence from the supports, will be uncovered, which can supply the theoretical guidance to the design and preparation of highly active catalysts for CO2 hydrogenation.

高活性催化剂是CO2高效加氢转化的关键，然而负载型CO2加氢催化剂的催化活性却难以显著提升。从催化剂工程的角度分析，目前普遍采用的负载型CO2加氢催化剂的制备必须涉及高温处理，以实现活性组分前驱体转化为催化活性组分，而如此活性组分的生成与大规模团聚结晶过程只能同步进行，这导致大部分负载组分无法形成高活性催化位点。针对上述问题，项目提出利用常温液相化学还原法生成均一非晶态负载活性组分，并与活性组分的结晶过程分立调控的方法制备负载型CO2加氢催化剂，在活性组分负载量一定的前提下，导向性地促进高活性催化位点的生成。通过考察不同制备参量对催化剂负载组分性质和催化活性的影响，揭示分立调控方法促进高活性位点生成的机制。通过量子化学模拟CO2在不同催化位点上的加氢行为，阐释不同活性位点与催化活性的构效关系，并揭示载体存在对活性位催化行为的影响，为有针对性地设计制备高活性CO2加氢催化剂提供理论指导。

碳吸附捕集和加氢转化是实现“碳中和”战略的两个重要手段。高吸附容量和吸附选择性的CO2吸附剂、高催化活性和催化选择性的CO2转化催化剂的制备是制约碳捕集和再利用的瓶颈。探究CO2吸附和催化转化的确切活性位点，探讨活性位点与其吸附、催化作用的构效关系，并在此基础上调控设计CO2吸附剂和催化剂，即有望突破上述制约瓶颈。本项目立足于碳吸附捕集和加氢转化两个层面，进行CO2吸附剂和加氢催化剂活性位调控提升机理以及新型吸附剂和催化剂的研究，包括：Cu-ZnO基CO2加氢催化剂的催化活性机理、Cu基金属有机骨架材料的调控与应用、CO2吸附位点与吸附性能构效关系、多孔碳材料中氮掺杂位点的CO2捕集能力。研究发现，Cu-ZnO二元组分中Cu/ZnO交界面和Zn掺杂的Cu晶面会在CO2加氢转化中相续起到活性位点的作用；Cu基卟啉金属有机骨架材料对于CO2加氢制醇类具有良好的催化活性和选择性，此外利用蒸汽诱导还原可在微孔Cu基金属有机骨架材料上调变出分级孔，从而赋予其更佳的吸附性能；CO2吸附剂中的氮掺杂位点是利用强范德华力来捕获CO2分子，利用超微孔的限域作用可以更好地捕获并限制CO2分子；利用定向设计的高含氮量的有机聚合物前驱体可构筑同时具备丰富微孔结构、高比表面积和高含氮量的氮掺杂多孔碳吸附剂，从而获取良好的CO2吸附容量和选择性。