杂化二维多孔金属有机材料的优化设计及特性和应用研究

Currently tremendous effort has been devoted to 2D atomic sheets based materials. The existing systems include graphene sheet and BN sheet. Manipulating the electronic structures of these 2D atomic sheets by introducing metal atoms for practical applications has been an important and challenging topic in this field. It has been found that the metal adatom migration activation barriers for the lowest energy migration paths on pristine monolayer, bilayer, and trilayer graphene are smaller than or within an order of magnitude of kBT (0.024eV) at room temperature, implying very high mobility for the adatoms. For example, the binding energy of a Cr atom with graphene is only 0.187 eV and the migration energy barrier is only 0.006 eV. This suggests that metal atoms evaporated onto graphene samples quickly migrate across the lattice and bind together forming clusters.The recent success in synthesizing 2D Fe-phthalocyanine (Pc) and Zn-porphyrin (P) porous sheets opens a new pathway to overcome the problem. However, the existing 2D organometallic sheets are mainly based on mono-metal units, which have the following shortcomings: First, the distance between metal ions are usually quite large, the concentration of metal ions is not high, so it is not very efficient for catalysis and gas molecule adsorptions; Second, due to the large distance the coupling between metal ions is weak, this is not good for the system to exhibit the cooperative effects like long-ranged ferromagnetic order with high Currie temperature and bimetallic catalytic effect; Third, there is no strong planar anisotropy, so the relevant physical and chemical processes are not selective and direction-dependent. These drawbacks can be overcome by hybridizing different structural units with different metals, which provides more variables to diversify the structures for tuning the properties and functionalities. The units that we use for the structures are already synthesized in experiments. At present there is no systematic study on such 2D hybrid organometallic sheets. This proposal would bridge this gap. We believe that this proposal is timely and of broad interest, and will motivate new experiments in this field.

在以石墨烯为代表的二维单原子层材料的研究浪潮中，近年来以金属钛菁为代表的金属-有机二维多孔材料异军突起，它不但合成方法灵活多变，而且具有有规分布的、未饱和配位的活性金属点位，这为催化、吸附等多领域的应用提供了新的候选材料。针对现有二维金属有机材料所存在的不足：基元单一， 活性金属位点浓度低；金属离子之间的距 离过大，使得相互间的耦合弱而不能产生协同效应（如强的铁磁序，优异的双金属催化效应），同时在面内缺少明显的各向异性使得所发生的物理化学过程不具有显著的方向性和选择性，我们首次系统开展"杂化二维多孔金属有机材料的优化设计及特性和应用研究"。通过高通量的计算模拟，优化结构单元之间的杂化方式、金属离子的空间排布和浓度，调节孔径大小，使得材料在磁性耦合、催化、储氢、二氧化碳捕获与转换等方面能表现出最佳性能，为新材料的实验合成提供理论依据和技术支撑。

不同于常规的二维材料（石墨烯，硅烯，硼烯，BN单层， MoS2, TiC2, 黑磷），金属-有机材料由于金属原子和有机配体的多样性和成键的灵活性，使得金属-有机二维多孔材料成为新型功能材料的研发对象。本课题在基金委的资助下，系统开展了由复杂配体的结构单元所形成的二维多孔材料的稳定性，电子能带结构，物理化学特性及其应用包括CO2的催化还原，量子拓扑结构，电池负极材料，二维双极磁性金属。这些研究不仅极大地扩展了二维材料体系，而且为新型能源材料，环境材料和多功能材料的研发提供了新的思路。