Superposition of dual electric fields in covalent organic frameworks for efficient photocatalytic hydrogen evolution  

共价有机框架双电场叠加实现高效光催化产氢

作　　者：Chao Li Shuo Wang Yuan Liub Xihe Huang Yan Zhuang Shuhong Wu Ying Wang Na Wen Kaifeng Wu Zhengxin Ding Jinlin Long 厉超;王朔;刘媛;黄细河;庄严;吴舒鸿;汪颖;温娜;吴凯丰;丁正新;龙金林(福州大学化学学院,能源与环境光催化国家重点实验室,福建福州350116;中国科学院大连化学物理研究所,分子反应动力学国家重点实验室,辽宁大连110623;福州大学化学学院,福建福州350116)

机构地区：[1]State Key Laboratory of Photocatalysis on Energy and Environment,College of Chemistry,Fuzhou University,Fuzhou 350116,Fujian,China [2]State Key Laboratory of Molecular Reaction Dynamics,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 110623,Liaoning,China [3]College of Chemistry,Fuzhou University,Fuzhou 350116,Fujian,China

出　　处：《Chinese Journal of Catalysis》2024年第8期164-175,共12页催化学报（英文）

基　　金：国家自然科学基金(22302038,22072022);福建省自然科学基金(2021L3003).

摘　　要：Covalent organic frameworks(COFs)are promising materials for converting solar energy into green hydrogen.However,limited charge separation and transport in COFs impede their application in the photocatalytic hydrogen evolution reaction(HER).In this study,the intrinsically tunable internal bond electric field(IBEF)at the imine bonds of COFs was manipulated to cooperate with the internal molecular electric field(IMEF)induced by the donor-acceptor(D-A)structure for an efficient HER.The aligned orientation of IBEF and IMEF resulted in a remarkable H_(2) evolution rate of 57.3 mmol·g^(-1)·h^(-1)on TNCA,which was approximately 520 times higher than that of TCNA(0.11 mmol·g^(-1)·h^(-1))with the opposing electric field orientation.The superposition of the dual electric fields enables the IBEF to function as an accelerating field for electron transfer,kinetically facilitat-ing the migration of photogenerated electrons from D to A.Furthermore,theoretical calculations indicate that the inhomogeneous charge distribution at the C and N atoms in TNCA not only pro-vides a strong driving force for carrier transfer but also effectively hinders the return of free elec-trons to the valence band,improving the utilization of photoelectrons.This strategy of fabricating dual electric fields in COFs offers a novel approach to designing photocatalysts for clean energy synthesis.光催化水分解制氢是解决环境污染和能源危机的理想途径.共价有机骨架(COFs)作为一类由共价键连接的周期性网状拓扑材料,其电子结构和化学性质可在分子水平上进行定制和调控,是研究半导体光催化剂构-效关系的理想模型.为了提高COFs的电荷分离效率,在COFs骨架上设计供体-受体(D-A)单元,构筑分子内电场(IMEF)促进电荷定向迁移是一种行之有效的策略.然而,在亚胺键连接的COFs中,亚胺键取向诱导产生的键内电场(IBEF)对光生激子的分离效率的影响往往被忽视.因此,进一步研究IMEF与IBEF之间的相互作用对COFs内光生电子转移动力学的影响具有重要意义,可为深入揭示光催化产氢机制提供关键信息.本文报道了一种基于COFs的双电场叠加策略,用于提高光催化产氢反应效率.首先,通过将有机单元的末端官能团进行互换,利用水热法成功制备了两种亚胺键取向相反的强D-A型COFs光催化剂,TNCA和TCNA.其中,官能团的微小变化保证了由D-A结构组成的IMEF方向和强度的一致性,可以使得在仅改变IBEF的情况下全面研究COFs的电子结构.X射线粉末衍射、傅里叶变换红外光谱、固体核磁以及X射线光电子能谱等结果证实了两种COFs的成功合成.随后,扫描电镜、透射电镜和氮气等温吸脱附曲线结果表明两种COFs均为介孔材料.紫外-可见漫反射光谱结果表明,所制备的催化剂具有良好的可见光吸收能力,结合莫特肖特基曲线结果,表明催化剂在热力学上均满足光催化产氢的要求.采用光致发光光谱、时间分辨荧光光谱、电子顺磁共振、光电流以及电化学阻抗研究了两种催化剂的载流子分离和转移行为,并且利用飞秒瞬态吸收光谱进一步明确了COFs中光生电荷转移动力学过程.结果表明,相较于TCNA,TNCA在光照下能够产生更多的光生电子且具有更长的寿命.光催化产氢活性评价结果显示,在可见光(λ�

关 键 词：Covalent organic framework Internal molecular electric field Internal bond electric field PHOTOCATALYSIS Hydrogen evolution 

分 类 号：TQ116.2[化学工程—无机化工] O643.36[理学—物理化学] O644.1[理学—化学]