Theory guided synthesis of MXenes with magnetic ordering

MXenes代表了一类二维材料，其一般化学成分为Mn+1XnTx (M =过渡金属，X = C， N, C/N, Tx =官能团，通常为-F， -OH, -O)，可以从三维MAX相（Mn+1AXn, a = IIIA /IVA族元素）中化学剥离，其性质可以通过其组成和表面功能化来调整。这种可变性及其独特的性质（金属导电性，亲水性，机械稳定性）在各种技术领域（储能，（光）催化，气体检测等）中具有许多潜在的应用。另一方面，尽管有许多原则上可能的组合物和大量现有的前体MAX相，但到目前为止，只有大约30个MXenes被成功合成。本项目的目标是在对各自前驱体MAX相的稳定性和可溶性进行广泛的理论计算的基础上制备新型的、理想磁性的MXenes。到目前为止，只有有限数量的二维磁性有序材料存在，然而，它们对潜在的自旋电子应用和量子材料非常感兴趣。基于它们的化学多样性（组成和表面功能化），预期的新材料有望显著扩展这类材料，同时增加有益的特性（例如形成稳定的胶体溶液），特别是在它们的加工和应用中。为了探索化学成分的空间，这将允许磁排序，尽可能充分，我们将结合实验和理论方法。在高通量电子结构计算和建立的热力学模型的基础上，我们将系统地研究和预测MAX相的稳定性及其在MXenes中的可溶性。项目实验部分的反馈将用于不断完善热力学模型和改进预测，如果适用的话。有前途的前驱体MAX相将通过多种固态和湿化学方法合成，如微波加热和溶胶-凝胶化学。这将导致三元和四元MAX相，随后将用不同的蚀刻剂处理，如果成功，剥离成它们的二维类似物。

MXenes represent a family of two-dimensional materials with the general chemical composition Mn+1XnTx (M = transition metal, X = C, N, C/N, Tx = functional groups, typically -F, -OH, -O) that can be chemically exfoliated from three-dimensional MAX phases (Mn+1AXn, A = group IIIA /IVA element) and whose properties can be tuned both by means of their composition and by surface functionalisation. This variability, together with their unique properties (metallic conductivity, hydrophilic, mechanical stability) has led to many potential applications within various technological fields (energy storage, (photo) catalysis, gas detection etc.). On the other hand, despite the many, in principle possible compositions and the large number of existing precursor MAX phases, only about 30 MXenes have been successfully synthesised so far. The goal of the here proposed project is the preparation of novel, ideally magnetic MXenes based on extensive theoretical calculations of the stability and exfoliability of respective precursor MAX phases. So far, only a limited number of two-dimensional materials with magnetic ordering exist, that are, however, highly interesting for potential spintronic applications and as quantum materials. Based on their chemical diversity (composition and surface functionalisation), the expected new materials promise to significantly extend this class of materials while adding beneficial properties (e.g. form stable colloidal solutions), particularly for their processing and applications. In order to explore the space of chemical compositions, that will allow for magnetic ordering, as fully as possible, we will combine experimental and theoretical methods. On the basis of high-throughput electronic-structure calculations and established thermodynamic models we will systematically investigate and predict the stability of MAX phases and their exfoliability into MXenes. Feedback from the experimental part of the project will be used to successively refine the thermodynamic models and improve predictions, if applicable. Promising precursor MAX phases will be synthesised by diverse solid-state and wet chemical methods, such as microwave heating and sol-gel chemistry. This will lead to ternary and quaternary MAX phases that will subsequently be treated with different etchants, and, if successful, exfoliated, into their two-dimensional analogs.