【Angew.Chem.】唐本忠院士团队华南理工秦安军|突破330℃！利用振动耦合分子工程实现有机材料创纪录的高温太阳能-热转换
文章标题：Molecular Engineering of Vibronic Coupling Enables High-Temperature Solar–Thermal Conversion in an Organic Material
通讯作者：Yaxin Zhai, Bin Hu, Anjun Qin
文章概要
太阳能-热转换是捕获太阳能最直接、最高效的途径之一。然而，传统有机光热材料由于受限于日光吸收能力弱、光热转换效率低及热稳定性差等瓶颈，工作温度普遍低于150℃，极大限制了其在高温工业领域（如聚焦太阳能发电系统）的应用。在这项工作中，研究团队通过分子工程巧妙地设计出一种具有D-≡-A-≡-D结构的新型有机光热小分子BTDyA。该材料在室外集中太阳光照射下，平衡温度可飙升至惊人的330℃，刷新了目前已报道的有机太阳能-热转换材料的最高温度纪录。在1064 nm激光照射下，其温度更可达到377℃，成功打通了有机材料走向高效高温太阳能捕获与能量存储的新通道。
引言
随着全球化石能源危机的加剧，如何高效开发和利用太阳能这一清洁、可持续的资源已成为科学界的核心课题。在诸多太阳能转化技术中，聚焦太阳能发电（CSP）技术利用反射镜将太阳光聚集并加热传热流体至300℃以上，展现出巨大的商业部署潜力。尽管无机非金属与金属材料在该领域占据统治地位，但有机材料凭借出色的结构可调性、良好的溶液加工性和较低的固有热导率，正逐渐成为极具竞争力的候选项。然而，如何在有机固态物质中同时实现全光谱强吸收、超快激发态非辐射跃迁以及极强的电子-振动耦合，从而跨越300℃的高温门槛，一直是制约该领域发展的科学难题。
FIGURE 1 Chemical structures, photophysical properties, thermal stability, and solar–thermal conversion properties of BTDyA, BTAyA, and BTDA. (a) Their chemical structures. (b) Their absorption spectra and the molar absorption coefficients (ε) in DMF solution (10 µM). (c) The UV/vis–NIR absorption spectra of their powders. (d) Their thermogravimetric analysis curves, recorded under nitrogen at a heating rate of 10 °C min−1. (e) The solar-thermal conversion equilibrium temperature of their powders (30 mg) under simulated solar light at different power densities.
主要实验及结论
为了解决这一难题，研究人员以具有强电子受体特征的[1,2,5]噻二唑并[3,4-f]苯并三唑为核心，通过引入炔键作为共轭π桥连接三苯胺供体，成功合成了对称型的BTDyA分子，如图1a所示。得益于炔键的引入，BTDyA不仅在溶液中展现出大幅提升的摩尔吸收系数，其固态粉末更表现出延伸至1500 nm的超宽光谱近红外吸收尾褶，如图1c所示，这为最大限度捕获太阳光奠定了物理基础。在光热性能测试中，BTDyA粉末在模拟太阳光及室外聚焦自然光的照射下展现出极其优异的升温响应，如图1e所示。在相同浓度的室外集中光照下，BTDyA迅速达到了330℃的历史最高光热平衡温度。
FIGURE 2 Comparison of solar–thermal conversion temperatures. The maximum solar–thermal conversion temperatures and corresponding time for reported organic materials under solar light at different irradiation intensities.
FIGURE 3 Photothermal conversion properties under NIR laser irradiation. (a) IR thermal images of BTDyA powder (30 mg) under 1064 nm laser irradiation at a power intensity of 1.8 W cm−2, and then turned off. (b) Photothermal conversion behavior of BTDyA powder under 1064 nm laser irradiation at different power densities (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, and 1.8 W cm−2). (c) Anti-photobleaching property of BTDyA powder under 1064 nm laser irradiation at a power intensity of 1.8 W cm−2 during five cycles of heating–cooling processes. The photothermal equilibrium temperatures of BTDyA, BTAyA, and BTDA powders (30 mg) under (d) 808 nm laser and (e) 1064 nm laser irradiation at different power densities.
FIGURE 4 Transient absorption and excited-state decay behavior. 3D fs-TA of (a) BTDyA, (b) BTAyA, and (c) BTDA powders in the 450–1600 nm at different time delays acquired after excitation at 400 nm. (d) Excited-state absorption (ESA) kinetic decay traces and corresponding fitting curves of BTDyA (at 544 nm), BTAyA (at 555 nm), and BTDA (at 533 nm). Ground-state bleach (GSB) kinetic decay traces and corresponding fitting curves of (e) BTDyA, BTAyA, and BTDA at 875 nm and (f) BTDyA, and BTAyA at 1064 nm.
为了探明其超高效光热转换的内在微观机制，研究团队借助飞秒瞬态吸收光谱和光诱导拉曼光谱对激子动力学及声子耦合进行了深度解密。如图4a所示，三维瞬态吸收光谱证实BTDyA粉末在受到激发后表现出最快的激发态自发衰减速率。这种超快的非辐射跃迁通路有效抑制了荧光发射等辐射损失，促使激子能量向振动能剧烈转化。更关键的是，功率依赖和温度依赖的拉曼光谱测试结果（如图5d和5g所示）表明，BTDyA在光激发下触发了极具代表性的骨架振动模式与晶格声子增强。这种强烈的电子-振动/声子耦合效应，赋予了材料将吸收入射光子高效转化为分子热运动能量的杰出本领，从而在宏观上表现出极其猛烈的温升行为。
FIGURE 5 Raman spectroscopy and molecular vibronic coupling characteristics. (a) Raman spectra of BTDyA, BTAyA, and BTDA. Regionally enlarged Raman spectra identifying key vibrational modes in (b) 850–880 cm−1, 1270–1320 cm−1, and (c) 100–200 cm−1 of BTDyA, BTAyA, and BTDA. Power-dependent Raman peak intensity variations of (d) BTDyA@862 cm−1, BTAyA@864 cm−1, BTDA@870 cm−1, (e) BTDyA@1292 cm−1, BTAyA@1291 cm−1, BTDA@1286 cm−1, (f) BTDyA@121 cm−1, BTAyA@137 cm−1, and BTDA@142 cm−1. (g) Regionally enlarged Raman spectra of BTDyA at different temperatures. Temperature-dependent Raman peak intensity variations of (h) BTDyA@862 cm−1, BTAyA@865 cm−1, BTDA@869 cm−1, (i) BTDyA@1292 cm−1, BTAyA@1289 cm−1, and BTDA@1286 cm−1.
最后，依托BTDyA优异的高温光热转换能力和优良的溶液加工便利性，研究人员开发出一种新型太阳能-热存储原型器件，并将其成功应用于熔融盐热能存储中。如图6a和6b所示，在18倍太阳光强度的室外自然光聚焦下，涂覆有BTDyA的器件表面温度迅速超越220℃，成功促使覆盖在表面的工业太阳能盐发生相变并完全熔融。而在切断光源后，熔融盐的潜在热能释放使整个器件维持了长期的温度缓释平台，如图6c所示，完美实现了太阳能转换与相变潜热存储的一体化集成。
FIGURE 6 Outdoor solar-thermal conversion and storage application. (a) Schematic diagram and digital photograph of the preparation of solar–thermal conversion devices and the process of solar–thermal melting of solar salts under concentrated outdoor sunlight. (b) IR thermal images and (c) temperature curve of solar–thermal conversion devices with/without solar salt loading under concentrated outdoor sunlight. (d) The part of cooling curves (60–76 s) and the cooling rate in different period.
总结及展望
该项研究成功推出了一种刷新历史纪录的高温有机太阳能-热转换材料BTDyA，并通过先进的光谱分析从本质上阐明了“超快激发态失活结合强电子-振动耦合”的高效产热机制。这一突破性成果不仅全面打破了有机材料无法胜任300℃以上高温光热领域的传统科学认知，还成功论证了其在太阳能高温集热和熔融盐储能技术中的实际应用可行性。面向未来，这种通过分子工程精确调控微观振动耦合的策略，将为开发下一代兼具高加工性、结构高度可定制性的先进光热转换器件与清洁能源集成系统提供极其关键的理论指导与技术支撑。