Precise tuning of interlayer electronic coupling in layered conductive metal-organic frameworks

Electrically conductive metal-organic frameworks (MOFs), such as two-dimensional conjugated MOFs (2D c-MOFs), have attracted increasing interests for (opto)-electronics and spintronics. They generally consist of van der Waals stacked layers and exhibit layer-depended electronic properties. While considerable efforts have been made to regulate the charge transport within a layer, precise control of electronic coupling between layers has not yet been achieved. The researchers from the group of Prof. Xinliang Feng report a novel strategy to precisely tune interlayer charge transport in 2D c-MOFs via side-chain induced control of the layer spacing. They design hexaiminotriindole ligands allowing programmed functionalization with tailored alkyl chains (HATI_CX, X = 1,3,4; X refers to the carbon numbers of the alkyl chains) for the synthesis of semiconducting Ni₃(HATI_CX)₂. The layer spacing of these MOFs can be precisely varied from 3.40 to 3.70 Å, leading to the widened band gap, suppressed carrier mobilities, and significant improvement of the Seebeck coefficient. With this demonstration, we further achieve a record-high thermoelectric power factor of 68 ± 3 nW m⁻¹ K⁻² in Ni₃(HATI_C3)₂, superior to the reported holes-dominated MOFs.

Reference: Yang Lu, Yingying Zhang, Chi-Yuan Yang, Sergio Revuelta, Haoyuan Qi, Chuanhui Huang, Wenlong Jin, Zichao Li, Victor Vega, Yannan Liu, Xing Huang, Darius Pohl, Miroslav Polozǐj, Shengqiang Zhou, Enrique Canovas, Thomas Heine, Simone Fabiano, Xinliang Feng, Renhao Dong. Nature Communications, 2022, 13, 7240.

Acknowledgements: We acknowledge cfaed and Dresden Center for Nano- analysis (DCN) at TUD. We acknowledge the financial support from ERC starting grant (FC2DMOF, No. 852909), EU Graphene Flagship (Core3, No. 881603), ERC Consolidator Grant (T2DCP), DFG projects (CRC-1415, No. 417590517; SPP-1928, COORNET), H2020-MSCA-ITN (ULTIMATE, No. 813036), EMPIR-20FUN03-COMET, H2020-FETOPEN (PROGENY, 899205) as well as the German Science Council and Center of Advancing Electronics Dresden (cfaed). R.D. thanks Taishan Scholars Program of Shandong Province (tsqn201909047). S.F. acknowledges support from the Swedish Research Council (2020-03243) and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU 2009-00971). Y. Z. acknowledges China Scholarship Council. Y. L. and Y. Z. acknowledge ZIH Dresden for computer time.