Influence of Ion Exchange on Photoresponsive Properties of Potassium Poly(heptazine imide),Chemistry of Materials

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Influence of Ion Exchange on Photoresponsive Properties of Potassium Poly(heptazine imide)
Chemistry of Materials ( IF 7.2 ) Pub Date : 2023-01-26 , DOI: 10.1021/acs.chemmater.2c03325
Mai Hattori ₁ , Miyu Nakamichi ₁ , Aika Yamaguchi ₁ , Chihiro Miyazaki ₁ , Goichiro Seo ₁ , Ryosuke Ohnuki ₁ , Shinya Yoshioka ₁ , Kaname Kanai ₁

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Metal poly(heptazine imide) (MPHI) exhibits various optoelectronic functions by accommodating various metal ions in its heptazine-based graphite-like two-dimensional layer. Although potassium PHI (KPHI) is the most well-studied in MPHI series, there are unresolved issues regarding the mechanism responsible for its unique properties, particularly its high photocatalytic activity. The mechanisms underlying other diverse properties, such as photochromism and photoconduction, also remain unknown. Herein, we focused on elucidating the mechanisms of photochromism and photoconduction in KPHI. We developed a method to gradually replace K⁺ in KPHI with H⁺ and successfully prepare samples with tunable K⁺ concentrations. The structural, chemical, optical, electronic, and electrical properties of samples with continuously varying K⁺ concentrations were thoroughly investigated through various experiments and theoretical calculations. First, the gradual substitution of K⁺ for H⁺ in KPHI was investigated using X-ray photoelectron spectroscopy, X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy. XRD analysis revealed that K⁺ in KPHI was not randomly substituted with H⁺, but even small amounts of K⁺ substitution led to the formation of the long-range ordered region of HPHI. Absorbance measurements revealed a continuous blue shift of the absorption edge as the ratio of K⁺ decreased from that of KPHI. Energy band calculations revealed that the energy gap of HPHI was more than 14% larger than that of KPHI. The dependence of the K⁺ concentration measurements on the photochromism and photoconductive properties showed that in the K⁺-rich samples, the K⁺ released from the PHI layer upon white light irradiation had a significant effect on the electrical conduction properties. K⁺ conduction was dominant in the electrical conduction of KPHI, including photoconduction, under ambient conditions. However, the mobility of H⁺ in HPHI was very low, which was responsible for the lethargic return to the ground state after photoexcitation and minimal electrical conductivity.

中文翻译：

离子交换对聚（庚嗪酰亚胺）钾光响应特性的影响

金属聚（庚嗪酰亚胺）（MPHI）通过在其基于庚嗪的类石墨二维层中容纳各种金属离子而表现出多种光电功能。尽管 PHI 钾 (KPHI) 是 MPHI 系列中研究最充分的，但关于其独特性质的机制，尤其是其高光催化活性，仍存在未解决的问题。其他不同特性的潜在机制，如光致变色和光电导，也仍然未知。在此，我们专注于阐明 KPHI 中光致变色和光电导的机制。^{我们开发了一种逐渐用H +}替换KPHI 中的K ^{+的方法，并成功制备了具有可调K}⁺的样品浓度。^{通过各种实验和理论计算，对具有连续变化的 K +}浓度的样品的结构、化学、光学、电子和电学特性进行了彻底研究。首先，使用 X 射线光电子能谱、X 射线衍射 (XRD) 和傅里叶变换红外光谱研究了 KPHI 中K ⁺逐渐取代H ^{+的情况。}XRD 分析表明，KPHI 中的 K ⁺并非随机被 H ⁺取代，但即使少量的 K ⁺取代也会导致 HPHI 长程有序区域的形成。吸光度测量显示吸收边的连续蓝移作为 K 的比率⁺低于 KPHI。能带计算表明，HPHI 的能隙比 KPHI 的能隙大 14% 以上。^{K +}浓度测量对光致变色和光导特性的依赖性表明，在富含 K ⁺的样品中，白光照射时从 PHI 层释放的 K ⁺对导电特性有显着影响。在环境条件下， K ⁺传导在 KPHI 的导电中占主导地位，包括光电导。^{然而，H +}在 HPHI 中的迁移率非常低，这是造成光激发后昏睡回到基态和最小电导率的原因。

更新日期：2023-01-26

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