金属有机框架载体内Ru(bda)L_(2)催化剂微环境的调控实现高效光驱动水氧化  

Microenvironment regulation of Ru(bda)L_(2)catalyst incorporated in metal‐organic framework for effective photo‐driven water oxidation

作　　者：冯坚信 李轩 罗宇成 苏志芳 钟茂灵 余宝蓝 石建英 Jianxin Feng;Xuan Li;Yucheng Luo;Zhifang Su;Maoling Zhong;Baolan Yu;Jianying Shi(School of Chemistry,Lehn Institute of Functional Materials,Sun Yat‐Sen University,Guangzhou 510275,Guangdong,China)

机构地区：[1]中山大学化学学院,莱恩功能材料研究所,广东广州510275

出　　处：《Chinese Journal of Catalysis》2023年第5期127-136,共10页催化学报（英文）

基　　金：国家重点基础研究发展计划(2021YFA1500401);国家自然科学基金(21875293,22075332,21890380).

摘　　要：人工光合作用研究中,因涉及多个电子和质子的转移而具有缓慢动力学特征的产氧半反应,是实现水全分解的关键.作为一类高效水氧化催化剂,Ru(bda)L_(2)(H_(2)bda=2,2’-联吡啶-6,6’-二羧酸,L=配体)分子催化剂被广泛应用于化学驱动的水氧化研究,其中O-O键的形成是水氧化反应的决速步骤.相比之下,因光敏剂和牺牲试剂的参与,光驱动水氧化反应的决速步骤为高价Ru物种的形成,且存在光敏剂自身氧化分解与光敏剂氧化催化中心成为高价Ru物种之间的竞争.因此,促进分子催化剂向光敏剂的多步非等价电子转移,是提高光催化水氧化性能的关键.自然光合作用中,水氧化过程中高效的质子传输和电子转移与光系统PSII中[Mn_(4)CaO_(5)]簇活性位点周围复杂的蛋白质微环境密切相关.因此,利用多孔载体实现Ru分子催化剂的固载,在多相化提高其稳定性的同时,为Ru催化剂周围微环境的调控提供了可能.基于本课题组前期发展的配位辅助自组装策略,本文将Ru(bda)L_(2)分子催化剂固载到金属-有机框架UiO-66载体中(Ru(bda)L_(2)@UiO-66),作为孤立的催化位点用于化学驱动和光驱动水氧化反应研究.在Ce^(4+)化学驱动水氧化反应中,Ru(bda)L_(2)@UiO-66表现出比均相体系更高的活性和稳定性.在以Ru(bpy)_(3)Cl_(2)为光敏剂,Na_(2)S_(2)O_(8)为牺牲剂的光催化体系,Ru(bda)L_(2)@UiO-66在磷酸盐缓冲水溶液中光驱动水氧化催化转化数高达566,比相同条件下的均相催化剂高出近20倍.进一步对比磷酸盐缓冲水溶液、硼酸盐缓冲水溶液和纯水三种溶剂中的光驱动水氧化性能,发现水氧化性能越高,因光敏剂氧化分解而产生的CO_(2)量越低.通过紫外-可见漫反射光谱、红外光谱、X射线粉末衍射和X射线光电子能谱等技术对反应前后催化剂的组成和结构进行研究,结果表明,在化学驱动水氧化反应前后Ru(bda)L_(2)@UiO-66结构保持不变;�A Ru(bda)L_(2)molecular catalyst(H_(2)bda=2,2′‐bipyridine‐6,6′‐dicarboxylic acid,L represents ligands)was incorporated into a UiO‐66 metal‐organic framework(MOF)as isolating sites for chemical‐and photo‐driven water oxidation with the water nucleophilic attack mechanism.An impressive turn‐over number of 566 was obtained for photo‐driven water oxidation in the phosphate buffer saline,which was nearly 20 times that of the homogenous counterpart in the presence of ruthenium tris(bipyridine)and sodium persulfate.Infrared spectroscopy,X‐ray diffraction and X‐ray spectroscopy techniques were used to characterize the composition and structure of the catalysts.Kinetic isotope effect(KIE),proton inventory experiment and proton nuclear magnetic resonance were conducted to understand the photo‐driven O_(2)evolution mechanism.It was observed that the protons participated in O_(2)evolution with a normal KIE value,and the uptake of phosphates by UiO‐66 matrix improved the affinity towards H_(2)O via hydrogen bonding.The high O_(2)output and the limited photosensitizer oxidative decomposition in PBS suggest that the phosphate acted as a proton mediator to assist proton and/or proton‐couple electron transfer through a hydrogen‐bonded network of water molecules.This study uses a heterogenous matrix to emulate an enzyme‐like microenvironment capable of achieving efficient artificial photosynthesis.

关 键 词：Ru(bda)L_(2)催化剂 隔离位点 光驱动水氧化 质子介质 微环境 

分 类 号：TQ426[化学工程] TQ116.2