Toffoli Daniele, Bernes Elisa, Cossaro Albano, Balducci Gabriele, Stener Mauro, Mauri Silvia, Fronzoni Giovanna
Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy.
CNR-IOM, Istituto Officina dei Materiali, I-34149 Trieste, Italy.
Nanomaterials (Basel). 2022 May 9;12(9):1610. doi: 10.3390/nano12091610.
The electronic properties of 2D boroxine networks are computationally investigated by simulating the NEXAFS spectra of a series of molecular models, with or without morphologic defects, with respect to the ideal honeycomb structure. The models represent portions of an irregular 2D boroxine framework obtained experimentally, as supported by the Au(111) surface. The B K-edge NEXAFS spectra are calculated within the transition potential (TP) approximation (DFT-TP). The role of the Au(111) supporting surface on the spectral features has also been investigated by comparing the calculated spectra of a defect-rich model in its free-standing and supported form. The calculated NEXAFS spectra differ from the experimental ones, as the position of the main resonance does not match in the two cases. This finding could suggest the presence of a strong interaction of the 2D boroxine network with the Au substrate, which is not captured in the model calculations. However, good agreement between measured and calculated B K-edge NEXAFS spectra is obtained for a model system, namely, trihydroxy boroxine, in which the B atoms are less screened by the valence electrons compared to the B-B linked boroxine network models considered here. These results suggest catalytic activity in the gold substrate in promoting a weakening or even the breaking of the B-B bond, which is not revealed by calculations.
通过模拟一系列分子模型（有无形态缺陷）相对于理想蜂窝结构的近边X射线吸收精细结构（NEXAFS）光谱，对二维硼氧环网络的电子性质进行了计算研究。这些模型代表了实验获得的不规则二维硼氧环框架的部分结构，由金（111）表面支撑。在跃迁势（TP）近似（密度泛函理论-TP）下计算硼K边NEXAFS光谱。还通过比较富缺陷模型在自由状态和支撑状态下的计算光谱，研究了金（111）支撑表面对光谱特征的作用。计算得到的NEXAFS光谱与实验光谱不同，因为两种情况下主要共振的位置不匹配。这一发现可能表明二维硼氧环网络与金基底之间存在强相互作用，而模型计算中未捕捉到这种相互作用。然而，对于一个模型体系，即三羟基硼氧环，测量和计算得到的硼K边NEXAFS光谱之间取得了良好的一致性，其中与本文考虑的B-B键连接的硼氧环网络模型相比，B原子受到价电子的屏蔽较少。这些结果表明金基底具有催化活性，可促进B-B键的弱化甚至断裂，而计算结果并未揭示这一点。
