Wang Jiande, Chen Tianyang, Jeon Mingyu, Oppenheim Julius J, Tan Bowen, Kim Jihan, Dincă Mircea
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
J Am Chem Soc. 2024 Jul 24;146(29):20500-20507. doi: 10.1021/jacs.4c06935. Epub 2024 Jul 15.
Two-dimensional conductive metal-organic frameworks (2D cMOFs) are an emerging class of crystalline van der Waals layered materials with tunable porosity and high electrical conductivity. They have been used in a variety of applications, such as energy storage and conversion, chemiresistive sensing, and quantum information. Although designing new conductive 2D cMOFs and studying their composition/structure-property relationships have attracted significant attention, there are still very few examples of 2D cMOFs that exhibit room-temperature electrical conductivity above 1 S cm, the value exhibited by activated carbon, a well-known porous and conductive material that serves in myriad applications. When such high conductivities are achieved, Ni-diamine linkages are often involved, yet Ni-diamine MOFs remain difficult to access. Here, we report two new 2D cMOFs made through ortho-diamine connections: M(HITT) (M = Ni, Cu; HITT = 2,3,7,8,12,13-hexaiminotetraazanaphthotetraphene). The electrical conductivity of Ni(HITT) reaches 4.5 S cm at 298 K, whereas the conductivity of Cu(HITT) spans from 0.05 (2CuCu) to 10 (3Cu) upon air oxidation, much lower than that of Ni(HITT). Spectroscopic analysis reveals that Ni(HITT) exhibits significantly stronger in-plane π-d conjugation and higher density of charge carriers compared to Cu(HITT), accounting for the higher electrical conductivity of Ni(HITT). Cu/Cu mixed valency modulates the energy level and carrier density of Cu(HITT), allowing for a variation of electrical conductivity over 4 orders of magnitude. This work provides a deeper understanding of the influence of metal nodes on electrical conductivity and confirms ortho-diamine linkers as privileged among ligands for 2D cMOFs.
二维导电金属有机框架（2D cMOFs）是一类新兴的晶体范德华层状材料，具有可调的孔隙率和高电导率。它们已被用于各种应用，如能量存储与转换、化学电阻传感和量子信息。尽管设计新型导电2D cMOFs并研究其组成/结构-性能关系已引起广泛关注，但室温电导率高于1 S/cm的2D cMOFs实例仍然很少，而1 S/cm是活性炭所表现出的值，活性炭是一种在众多应用中使用的著名多孔导电材料。当实现如此高的电导率时，通常涉及镍-二胺键，但镍-二胺MOFs仍然难以获得。在此，我们报道了通过邻二胺连接制备的两种新型2D cMOFs：M(HITT)（M = Ni、Cu；HITT = 2,3,7,8,12,13-六亚氨基四氮杂萘并四苯）。Ni(HITT)在298 K时的电导率达到4.5 S/cm，而Cu(HITT)在空气氧化后的电导率范围为0.05（2CuCu）至10（3Cu），远低于Ni(HITT)。光谱分析表明，与Cu(HITT)相比，Ni(HITT)表现出明显更强的面内π-d共轭和更高的电荷载流子密度，这解释了Ni(HITT)具有更高的电导率。Cu/Cu混合价态调节了Cu(HITT)的能级和载流子密度，使得电导率变化超过4个数量级。这项工作提供了对金属节点对电导率影响的更深入理解，并证实邻二胺连接体是2D cMOFs配体中的优势连接体。
