In photocatalysis, it is of general interest to understand and design wide-range light-absorbing inorganic/organic hybrid materials with an excellent photo-induced intramolecular charge-transfer (ICT) effect. To verify the role of unpaired electrons in enhancing ICT within electron-withdrawing ligand-based metal–organic frameworks (MOFs), the molecular structure, density of states (DOS), and electronic structure of strong electron-deficient pyridine-diketopyrrolopyrrole (P-DPP)-based Zn (or Cu) MOFs were calculated in Gaussian package to validate the unpaired electron ICT. The electron spin resonance technique has detected the unpaired electrons for the coordination systems containing Zn–O or Cu–O clusters and P-DPP ligand on photoexcitation. The estimated band gaps from the DOS calculation for P-DPP-Cu and P-DPP-Zn are 1.4 and 2.4 eV, respectively, showing a good agreement with the experimental UV–vis optical spectra. The partial DOS, dipole moment, and frontier orbital analysis prove that the ICT should happen from Zn–O or Cu–O clusters to P-DPP ligands. This research may contribute to a comprehensive understanding of electron-withdrawing ligand-induced ICT within MOFs and shed light on the design of light-absorbing MOFs with excellent ICT or conductivity.

中文翻译：

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含吸电子配体的Zn（或Cu）MOF中不成对电子诱导的宽范围光吸收：理论和实验研究。

在光催化中，人们普遍了解并设计具有出色光致分子内电荷转移（ICT）效果的宽范围吸光无机/有机杂化材料。在不吸电子的配体基金属有机框架（MOFs），强电子缺陷型吡啶-二酮吡咯并吡咯（P-）的分子结构，态密度（DOS）和电子结构中验证未配对电子在增强ICT中的作用在高斯软件包中计算了基于DPP的Zn（或Cu）MOF，以验证未配对的电子ICT。电子自旋共振技术已经检测到包含Zn–O或Cu–O团簇和P-DPP的配位系统的未配对电子光激发下的配体。从DOS计算得出的P-DPP-Cu和P-DPP-Zn的估计带隙分别为1.4和2.4 eV，与实验紫外可见光谱具有很好的一致性。部分DOS，偶极矩和边界轨道分析证明ICT应该从Zn-O或Cu-O簇到P-DPP配体发生。这项研究可能有助于对MOF中吸电子配体诱导的ICT的全面理解，并有助于设计具有出色ICT或导电性的吸光MOF。