Improving the response of 2D COFs to the surface doping strategies through rational design of their chemical structure

通过二维COF化学结构的设计提高其对表面掺杂策略的响应

The chemical structure of covalent organic frameworks(COFs)plays a key role in their response to the surface doping strategy used for tuning their electronic character,but it is still not fully understood.To explore a rational design proposal for their chemical structure,the electronic properties of three n-doped typical COFs,including boroncontaining(COF-1),triazine-based(CTF),and C–C bondlinked(GCOF)COFs,were investigated theoretically in this work.As expected,the chemical doping effects are different for these COFs.The dispersion of the frontier bands,the nuclear-independent chemical shift(NICS)aromaticity index results,distribution of the electron localization function(ELF),and Hirshfeld charge population plots show that part of the transferred electron from dopants will be offset by the intralayer charge transfer of COFs.Thus,chemical doping effects are more significant if the electron distribution in the COFs is more localized.This means the response of COFs to the surface doping strategy should be dominated by the conjugation degree of their chemical structure.Our results prove that the intrinsic conjugation degree of COFs plays a key role in such doping functionalization strategies,which are expected to provide more useful information for the initial structure design of COF materials and facilitate their practical applications as active electronic transport materials in nanoscale devices.

共价有机框架(COFs)的化学结构在对用于调整它的电子特性的表面掺杂策略的响应中起着关键作用,但至今仍未完全了解.为了探索合理的化学结构设计方案,本研究中,从理论层面上揭示了三种n型掺杂典型COF的电子特性,该三种掺杂包括含硼COF-1、基于三嗪的COF(CTF)和C–C键连接的COF(GCOF).在我们的预测之中,这些COF的化学掺杂效应各不相同.前沿能带色散、NICS芳香指数的结果、电子局域化函数分布和Hirshfeld电荷分布图表明,来自掺杂剂的部分转移电子将被COFs的层内电荷转移所抵消,因此,如果COFs的电子分布更加局域化,化学掺杂效应就会更加显著.这意味着COF对表面掺杂策略的响应会受它的化学结构共轭度的影响.我们的研究结果证明,COFs的本征共轭度在这种掺杂功能化策略中起着关键作用,有望为COF材料的初始结构设计提供更多有用信息,进而促进其作为电子传输材料在纳米尺度器件中的实际应用.