文献类型：期刊文献

英文题名：Local Electronic Structure of a Single-Layer Porphyrin-Containing Covalent Organic Framework

作者：Chen, Chen[1];Joshi, Trinity[2];Li, Huifang[3];Chavez, Anton D.[4,5];Pedramrazi, Zahra[2];Liu, Pei-Nian[6,7];Li, Hong[3,8,9];Dichtel, William R.[4];Bredas, Jean-Luc[3,8,9];Crommie, Michael F.[2,10,11,12]

机构：[1]Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA;[2]Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA;[3]King Abdullah Univ Sci & Technol, Phys Sci & Engn Div, Lab Computat & Theoret Chem Adv Mat, Thuwal 239556900, Saudi Arabia;[4]Northwestern Univ, Dept Chem, Evanston, IL 60208 USA;[5]Cornell Univ, Dept Chem & Chem Biol, Ithaca, NY 14853 USA;[6]East China Univ Sci & Technol, Shanghai Key Lab Funct Mat Chem, 130 Meilong Rd, Shanghai 200237, Peoples R China;[7]East China Univ Sci & Technol, Sch Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China;[8]Georgia Inst Technol, Sch Chem & Biochem, 901 Atlantic Dr NW, Atlanta, GA 30332 USA;[9]Georgia Inst Technol, Ctr Organ Photon & Elect, 901 Atlantic Dr NW, Atlanta, GA 30332 USA;[10]Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA;[11]Univ Calif Berkeley, Kavli Energy NanoSci Inst, Berkeley, CA 94720 USA;[12]Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA

年份：2018

卷号：12

期号：1

起止页码：385

外文期刊名：ACS NANO

收录：;EI(收录号：20180804821854);WOS:【SCI-EXPANDED(收录号:WOS:000423495200041)】；

基金：This research was supported by the Army Research Office Multidisciplinary University Research Initiative (MURI) program under Grant No. W911NF-15-1-0447 (STM spectroscopy, precursor synthesis), by the Army Research Office Grant No. W911NF-17-1-0339 to Georgia Tech (DFT calculations), and by the U.S. Department of Energy, Office of Basic Energy Sciences, Nanomachine Program under Contract No. DEAC02-05CH11231 (sample preparation). The KAUST IT Research Computing Team and the KAUST Supercomputing Laboratory are gratefully acknowledged for providing generous computational resources for part of our theoretical work. T.J. acknowledges support from NSF Graduate Research Fellowship Program under Grant No. DGE 1106400. A.D.C. acknowledges support from the NDSEG Fellowship Program.

语种：英文

外文关键词：covalent organic framework; scanning tunneling microscopy and spectroscopy; density functional theory; electronic structure; porphyrin

摘要：We have characterized the local electronic structure of a porphyrin-containing single-layer covalent organic framework (COF) exhibiting a square lattice. The COF monolayer was obtained by the deposition of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMA) and 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP) onto a Au(111) surface in ultrahigh vacuum followed by annealing to facilitate Schiff-base condensations between monomers. Scanning tunneling spectroscopy (STS) experiments conducted on isolated TAPP precursor molecules and the covalently linked COF networks yield similar transport (HOMO-LUMO) gaps of 1.85 +/- 0.05 eV and 1.98 +/- 0.04 eV, respectively. The COF orbital energy alignment, however, undergoes a significant downward shift compared to isolated TAPP molecules due to the electron-withdrawing nature of the imine bond formed during COF synthesis. Direct imaging of the COF local density of states (LDOS) via dI/dV mapping reveals that the COF HOMO and LUMO states are localized mainly on the porphyrin cores and that the HOMO displays reduced symmetry. DFT calculations reproduce the imine-induced negative shift in orbital energies and reveal that the origin of the reduced COF wave function symmetry is a saddle-like structure adopted by the porphyrin macrocycle due to its interactions with the Au(111) substrate.