TEMPO显著加速芘基金属有机框架光催化硫化物到亚砜的转化  

TEMPO radically expedites the conversion of sulfides to sulfoxides by pyrene‐based metal‐organic framework photocatalysis

作　　者：曾冰 黄凤伟 王月欣 熊康慧 郎贤军 Bing Zeng;Fengwei Huang;Yuexin Wang;Kanghui Xiong;Xianjun Lang(Hubei Key Laboratory on Organic and Polymeric Optoelectronic Materials,College of Chemistry and Molecular Sciences,Wuhan University,Wuhan 430072,Hubei,China)

机构地区：[1]武汉大学化学与分子科学学院,湖北省有机高分子光电功能材料重点实验室,湖北武汉430072

出　　处：《Chinese Journal of Catalysis》2024年第3期226-236,共11页催化学报（英文）

基　　金：国家自然科学基金(22072108,22372124).

摘　　要：随着全球对可再生能源的需求持续上升,太阳能因其无限、清洁和可持续的特点被视为最理想的能源之一.在太阳能转化为化学能的过程中,半导体光催化技术因能够有效利用太阳能驱动化学反应而受到广泛关注.金属有机框架(MOF)因具有类似半导体的性质而广泛应用于光催化领域.然而,MOF在光催化选择性催化上仍存在活性低或选择性差等问题.为解决上述问题,加入氧化还原介质成为一个潜在的解决方案.通过深入研究氧化还原介质与MOF之间的协同作用,有望提升光催化选择性氧化的效率,从而推动MOF在光催化领域的应用发展.本文将炔基整合到芘基配体中,进一步调节金属有机框架的可见光吸收性质.具体来说,以4-苯基苯甲酸作为调节剂,由4,4',4'',4'''-(芘-1,3,6,8-四基四(乙炔-2,1-二基))四苯甲酸和Zr_(6)O_(4)(OH)_(4)^(12+)团簇合成了芘基MOF,即NU-1100,并采用粉末晶体衍射、氮气吸附-脱附、扫描电镜与透射电镜对结构进行表征.结果表明,由于拓宽配体的共轭结构,与NU-1000相比,NU-1100的可见光吸收带红移.实验结果表明,在光催化体系中加入氧化还原介质2,2,6,6-四甲基哌啶-N-氧化物(TEMPO)可以显著加速有机硫化物到亚砜的转化.在绿光照射下,体系中加入催化量(3 mol%)氧化还原介质TEMPO和4-羧基TEMPO后,转化率分别是单独使用NU-1100的2.7倍和5.2倍.而NU-1000由于不吸收绿光无法驱动硫化物的氧化.动力学研究结果表明,4-羧基TEMPO可以加速硫化物转化为亚砜的反应进程.光电化学测试结果表明,4-羧基TEMPO可以促进NU-1100光生电子和空穴的分离以及转移.利用密度泛函理论计算和一系列结构表征手段,研究了加入4-羧基TEMPO提高NU-1100光催化活性的原因.结果表明,4-羧基TEMPO吸附在NU-1100的Zr_(6)O_(4)(OH)_(4)^(12+)团簇外表面,介导了空穴的转移,实现了更高的电荷转移效率.通过猝灭实验和原位电子顺Metal-organic frameworks(MOFs)are well-documented for visible light photocatalysis because of their tailorable structures and tunable absorptions through organic linkers.By employing a highly conjugated linker,4,4',4'',4'''-(pyrene-1,3,6,8-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid,the optical absorption of the MOF NU-1100 is effectively tuned to visible light below 600 nm region.Under green light irradiation,NU-1100 triggers charge separation and modulates electron transfer from the linkers to the Zr_(6)O_(4)(OH)_(4)^(12+)clusters,driving the oxidation of sulfides to sulfoxides.Notably,adding a redox mediator radically expedites the oxidation of sulfides by NU-1100 photocatalysis,TEMPO(2,2,6,6-tetramethylpiperidine-N-oxyl)and 4-carboxy-TEMPO.At least 2.7 and 5.2 times of conversions of phenyl methyl sulfide are achieved by NU-1100 photocatalysis with TEMPO and 4-carboxy-TEMPO,respectively.A series of characterizations illustrate that 4-carboxy-TEMPO is adsorbed onto the exterior surface of Zr_(6)O_(4)(OH)_(4)^(12+)clusters of NU-1100 to mediate hole transfer and achieve higher charge transfer efficiency.Mechanistic studies indicate that superoxide is the essential reactive oxygen species and that the oxidation of sulfides is driven by an electron transfer pathway.This study demonstrates the integration of redox mediators with MOFs can drive more efficient visible light photocatalytic reactions.

关 键 词：金属有机框架 氧化还原介质 绿光 选择性氧化 光催化 

分 类 号：O643.36[理学—物理化学] O644.1[理学—化学]