含錸聯吡啶錯合物之線性共軛高分子應用於光驅動二氧化碳還原反應

Abstract

本研究成功設計並合成四種含聯吡啶和苯並噻二唑單元的線性共軛高分子(P1−P4)，其中P3與P4進一步螯合錸 (Re) 金屬，探討其於光驅動二氧化碳還原反應中的結構特性與催化表現。高分子經Suzuki與Stille耦合反應製備，並以衰減全反射紅外光譜儀、固態核磁共振光譜儀、X光光電子能譜與感應耦合電漿質譜儀等分析確認其結構與金屬組成。吸收光譜與循環伏安法結果指出，金屬錯合與共軛鏈段延伸可提升光吸收能力並降低能隙，有助於光生電子參與 CO2 還原反應。在光催化CO2 還原實驗中，P3與P4在CO2還原為CO的催化週轉數 (turnover number，TON) 分別達到60.7與52.1，明顯優於未螯合金屬的P1 (TON = 7.4) 與P2 (未檢出CO) 及傳統小分子 [fac-Re(bpy) (CO)3Cl] (ReBpy, TON = 14.4)，證明同時引入共軛高分子骨架及金屬中心能有效提升電子傳輸效率與整體催化效率。控制實驗與 13CO2 同位素標記實驗進一步證實產物確實來自 CO2 還原。光響應電流測試亦顯示P3與P4具備最佳的光生載子分離與傳輸能力，與其高催化效率相互呼應。此外，在多輪循環測試中，P3 與 P4 均展現優異的穩定性與可重複使用性，成功克服了傳統ReBpy小分子催化劑在光照下易生成Re−Re二聚體而失活的問題，顯示高分子主鏈所帶來的立體位阻與配位穩定性有助於抑制Re−Re二聚化反應，延長催化劑壽命。本成果為發展高效且耐久的光催化CO2還原材料提供了新策略與實驗依據。

In this study, four linear conjugated polymers (P1−P4) incorporating bipyridine and benzothiadiazole units have been synthesized. Among them, P3 and P4 are further coordinated with rhenium (Re) complexes to investigate their photocatalytic performance toward CO2 reduction. The polymers have been prepared via Suzuki and Stille coupling reactions, and their structures and metal compositions are confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy, solid-state nuclear magnetic resonance, X-ray photoelectron spectroscopy and inductively coupled plasma mass spectrometry. UV−Vis absorption and cyclic voltammetry show that both metal coordination and π-conjugation extension enhance light absorption and reduce the band gap. Photocatalytic experiments demonstrate that P3 and P4 achieve turnover numbers (TON) of 60.7 and 52.1 for CO generation, respectively, significantly outperforming the non-metal-chelated polymers P1 (TON = 7.4) and P2 (no detection of CO), as well as the traditional molecular catalyst [fac-Re(bpy) (CO)3Cl] (ReBpy, TON = 14.4). Control experiments and 13CO2 isotope labeling confirm that the CO product originates from CO2 reduction. Photocurrent measurements further reveal that P3 and P4 exhibit the most efficient photogenerated charge separation and transport. Moreover, both P3 and P4 display excellent reusability and stability across multiple reaction cycles, successfully overcoming the Re−Re dimerization-induced deactivation typically observed in small-molecule ReBpy systems. This improvement is attributed to the steric hindrance and coordination stability imparted by the polymer backbone, which effectively suppresses Re−Re aggregation and prolongs catalyst lifetime. Overall, this work provides a promising design strategy and experimental basis for the development of efficient and durable polymer-based photocatalysts for CO2 reduction.