Mohata Shibani, Das Risov, Koner Kalipada, Riyaz Mohd, Das Kousik, Chakraborty Subhajit, Ogaeri Yutaro, Nishiyama Yusuke, C Peter Sebastian, Banerjee Rahul
Department of Chemical Sciences, Indian Institute of Science Education and Research, Kolkata, Mohanpur 741246, India.
Centre for Advanced Functional Materials, Indian Institute of Science Education and Research, Kolkata, Mohanpur 741246, India.
J Am Chem Soc. 2023 Nov 1;145(43):23802-23813. doi: 10.1021/jacs.3c08688. Epub 2023 Oct 23.
The conversion of CO to a sole carbonaceous product using photocatalysis is a sustainable solution for alleviating the increasing levels of CO emissions and reducing our dependence on nonrenewable resources such as fossil fuels. However, developing a photoactive, metal-free catalyst that is highly selective and efficient in the CO reduction reaction (CORR) without the need for sacrificial agents, cocatalysts, and photosensitizers is challenging. Furthermore, due to the poor solubility of CO in water and the kinetically and thermodynamically favored hydrogen evolution reaction (HER), designing a highly selective photocatalyst is challenging. Here, we propose a molecular engineering approach to design a photoactive polymer with high CO permeability and low water diffusivity, promoting the mass transfer of CO while suppressing HER. We have incorporated a contorted triptycene scaffold with "internal molecular free volume (IMFV)" to enhance gas permeability to the active site by creating molecular channels through the inefficient packing of polymer chains. Additionally, we introduced a pyrene moiety to promote visible-light harvesting capability and charge separation. By leveraging these qualities, the polymer exhibited a high CO generation rate of 77.8 μmol g h, with a high selectivity of ∼98% and good recyclability. The importance of IMFV was highlighted by replacing the contorted triptycene unit with a planar scaffold, which led to a selectivity reversal favoring HER over CORR in water. electron paramagnetic resonance (EPR), time-resolved photoluminescence spectroscopy (TRPL), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques, further supported by theoretical calculations, were employed to enlighten the mechanistic insight for metal-free CO reduction to exclusively CO in water.
利用光催化将一氧化碳转化为单一碳质产物，是缓解一氧化碳排放不断增加以及减少我们对化石燃料等不可再生资源依赖的可持续解决方案。然而，开发一种在一氧化碳还原反应（CORR）中具有高选择性和高效性、无需牺牲剂、助催化剂和光敏剂的光活性无金属催化剂具有挑战性。此外，由于一氧化碳在水中的溶解度低以及动力学和热力学上有利于析氢反应（HER），设计一种高选择性光催化剂具有挑战性。在此，我们提出一种分子工程方法来设计一种具有高一氧化碳渗透性和低水扩散率的光活性聚合物，促进一氧化碳的传质同时抑制析氢反应。我们引入了具有“内部分子自由体积（IMFV）”的扭曲三蝶烯支架，通过聚合物链的低效堆积形成分子通道，从而提高气体向活性位点的渗透性。此外，我们引入了芘基团以提高可见光捕获能力和电荷分离。通过利用这些特性，该聚合物表现出77.8 μmol g⁻¹ h⁻¹的高一氧化碳生成速率，具有约98%的高选择性和良好的可回收性。用平面支架取代扭曲三蝶烯单元突出了内部分子自由体积的重要性，这导致在水中析氢反应比一氧化碳还原反应更受青睐的选择性反转。采用电子顺磁共振（EPR）、时间分辨光致发光光谱（TRPL）和漫反射红外傅里叶变换光谱（DRIFTS）技术，并辅以理论计算，以深入了解在水中无金属将一氧化碳还原为纯一氧化碳的机理。
