摘要
Two-dimensional covalent organic frameworks(2D COFs)feature extendedπ-conjugation and ordered stacking sequence,showing great promise for high-performance photocatalysis.Periodic atomic frameworks of 2D COFs facilitate the in-plane photogenerated charge transfer,but the precise ordered alignment is limited due to the non-covalentπ-stacking of COF layers,accordingly hindering out-of-plane transfer kinetics.Herein,we address a chiral induction method to construct a parallelly superimposed stacking chiral COF ultrathin shell on the support of SiO_(2) microsphere.Compared to the achiral COF analogues,the chiral COF shell with the parallel AA-stacking structure is more conducive to enhance the built-in electric field and accumulates photogenerated electrons for the rapid migration,thereby affording superior photocatalytic performance in hydrogen evolution from water splitting.Taking the simplest ketoenamine-linked chiral COF as a shell of SiO_(2) particle,the resulting composite exhibits an impressive hydrogen evolution rate of 107.1 mmol g^(-1)h^(-1)along with the apparent quantum efficiency of 14.31%at 475 nm.Furthermore,the composite photocatalysts could be fabricated into a film device,displaying a remarkable photocatalytic performance of 178.0 mmol m^(-2)h^(-1)for hydrogen evolution.Our work underpins the surface engineering of organic photocatalysts and illustrates the significance of COF stacking structures in regulating electronic properties.
光催化分解水是利用太阳能生产氢燃料的重要方法,可以有效解决能源危机问题,实现碳中和目标.二维共价有机框架(2DCOF)因其可调的化学结构、有序的堆叠排列和扩展的π共轭平面,成为极具应用前景的太阳能制氢光催化剂.光催化剂的效率在很大程度上依赖于其表面的性质,增强光催化剂表面电子性质对于有效的光生电荷分离和转移至关重要.2DCOF的周期性原子框架能够促进面内光生电荷的分离传输,然而,由于COF层间的非共价键相互作用,难以实现精确的有序排列,使得面间电子转移动力学受到限制.因此,通过调控COF的堆叠方式和表面电子性质来提高其光催化产氢效率,是一个重要且具有挑战性的研究方向.我们前期工作表明,通过手性诱导合成的2D COF能够形成平行AA-堆叠的精确层间排列(J.Am.Chem.Soc.,2024,146,13201-13209).本文将手性诱导与模板剂法结合构建了具有超薄手性COF壳层的纳米核壳结构.利用光惰性的SiO_(2)微球为模板通过亚胺反应在其表面形成一层无序的手性聚甲亚胺网络,随后在溶剂热的处理下引发原位的结晶结构转变和手性诱导重排,制得的COF壳层具有平行的AA堆叠排列、高结晶性和多孔性以及可控的尺寸和形貌,壳层厚度在3-60 nm间可调.光催化结果表明,该手性壳层能够实现较好的产氢性能,产氢速率可达107.1 mmolg~(-1)h^(-1),是非手性壳层的~2倍,且材料在可见光连续辐照40 h依旧能够稳定产氢.同时,手性复合微球在475 nm下的最大表观量子效率高达14.31%,高于目前报道的大多数COF基光催化剂.复合微球良好的水分散性使其能够进一步制成贴近实际应用生产的光催化薄膜器件,光照下可以从薄膜表面观察到丰富的氢气泡,其产氢速率达到178.0 mmol m^(-2)h^(-1).结合光物理特性和理论计算的机理研究揭示了手性诱导的AA-堆叠序列有利于促进堆叠原子之间的偶极�
基金
国家自然科学基金(52173197,52373202).
