Controlling Charge Transport in 2D Conductive MOFs─The Role of Nitrogen-Rich Ligands and Chemical Functionality
Petru Apostol, Sai Manoj Gali, Alice Su, Da Tie, Yan Zhang, Shubhadeep Pal, Xiaodong Lin, Vasudeva Rao Bakuru, Darsi Rambabu, David Beljonne, Mircea Dincă, Alexandru Vlad
Abstract
High Resolution Image Download MS PowerPoint Slide Two-dimensional electrically conducting metal–organic frameworks (2D-e-MOFs) have emerged as a class of highly promising functional materials for a wide range of applications. However, despite the significant recent advances in 2D-e-MOFs, developing systems that can be postsynthetically chemically functionalized, while also allowing fine-tuning of the transport properties, remains challenging. Herein, we report two isostructural 2D-e-MOFs: Ni 3 (HITAT) 2 and Ni 3 (HITBim) 2 based on two new 3-fold symmetric ligands: 2,3,7,8,12,13-hexaaminotriazatruxene (HATAT) and 2,3,8,9,14,15-hexaaminotribenzimidazole (HATBim), respectively, with reactive sites for postfunctionalization. Ni 3 (HITAT) 2 and Ni 3 (HITBim) 2 exhibit temperature-activated charge transport, with bulk conductivity values of 44 and 0.5 mS cm –1, respectively. Density functional theory analysis attributes the difference to disparities in the electron density distribution within the parent ligands: nitrogen-rich HATBim exhibits localized electron density and a notably lower lowest unoccupied molecular orbital (LUMO) energy relative to HATAT. Precise amounts of methanesulfonyl groups are covalently bonded to the N–H indole moiety within the Ni 3 (HITAT) 2 framework, modulating the electrical conductivity by a factor of ∼20. These results provide a blueprint for the design of porous functional materials with tunable chemical functionality and electrical response.