物理化学学报 >> 2024, Vol. 40 >> Issue (9): 2308019.doi: 10.3866/PKU.WHXB202308019

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超短c轴盘簇L沸石介晶的晶种诱导合成：形貌控制、解耦机理和增强吸附

严珂欣1, 叶兆祺1, 孔令涛1, 李贺1, 杨雪1, 张亚红1, 张宏斌1,2,*(), 唐颐1,*()   

  1. 1 复旦大学化学系, 上海市分子催化和功能材料重点实验室, 先进材料实验室, 能源材料化学协同创新中心, 上海 200433
    2 复旦大学中华古籍保护研究院, 图书馆, 上海 200433
  • 收稿日期:2023-08-12 修回日期:2023-10-02 录用日期:2023-10-09 发布日期:2023-10-18
  • 通讯作者: Email: yitang@fudan.edu.cn; Tel.: +86-13501616724 (唐颐)zhanghongbin@fudan.edu.cn; Tel.: +86-15921446296 (张宏斌)
  • 基金资助:
    国家重点研发计划(2018YFA0209402); 国家自然科学基金(22175040); 国家自然科学基金(22175040)

Seed-Induced Synthesis of Disc-Cluster Zeolite L Mesocrystals with Ultrashort c-Axis: Morphology Control, Decoupled Mechanism, and Enhanced Adsorption

Kexin Yan1, Zhaoqi Ye1, Lingtao Kong1, He Li1, Xue Yang1, Yahong Zhang1, Hongbin Zhang1,2,*(), Yi Tang1,*()   

  1. 1 Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai 200433, China
    2 Institute for Preservation of Chinese Ancient Books, Fudan University Library, Fudan University, Shanghai 200433, China
  • Received:2023-08-12 Revised:2023-10-02 Accepted:2023-10-09 Published:2023-10-18
  • Contact: Email: yitang@fudan.edu.cn; Tel.: +86-13501616724 (Yi Tang)zhanghongbin@fudan.edu.cn; Tel.: +86-15921446296 (Hongbin Zhang)
  • Supported by:
    the National Key R&D Program of China(2018YFA0209402); the National Natural Science Foundation of China(22175040); the National Natural Science Foundation of China(22175040)

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摘要：

缩短沸石材料的微孔孔道能有效提升客体分子的扩散传质性能。但目前一维L沸石(LTL)的合成中，缩短其沿一维微孔孔道方向(c轴方向)的长度至20到50 nm仍是一个挑战。本文首次在简单无机体系中通过加入纳米棒簇状L沸石作为晶种，快速(仅需4 h)合成了一种新型的L沸石介观结构晶体，且无需外加任何晶化修饰剂与模板剂。该介晶呈现出一种由超薄(约29 nm)的圆盘纳米晶沿c轴定向堆叠而成的盘簇形貌。这一独特的晶种诱导策略能够有效解耦L沸石的成核和生长阶段，为精确调控每个阶段的晶化行为以获得所需形貌结构提供了更大的操作空间。通过分析合成体系中介观尺度的晶核和微观尺度的基本构建单元衍化规律，实现了对晶种具体作用及衍化规律的解构：晶种溶解出的环笼结构加速了凝胶有序化，缩短了诱导期；而晶种溶解后的残余部分为生长期提供了密集的初始晶核，导向了新型盘簇结构的形成。通过对沸石生长条件进行调节，证实了其生长期存在蠕虫状前驱颗粒组装的行为，并实现了对盘簇中圆盘沿c轴方向厚度在18到55 nm范围内的精细调控。此外，通过选择直径为0.43到4.5 nm的系列模型分子作为吸附质，证明了该超短c轴样品在气相和液相体系大幅增强的吸附应用潜力。样品在小分子的扩散速率和大分子在气相的吸附量方面确实具有优势。在实际应用中，该样品在芳烃的吸附和分离以及染料和蛋白质的吸附方面具有一定的优势。

关键词: L沸石, 晶化机理, 非经典晶化机理, 形貌调控, 吸附性能, 晶种法

Abstract:

Zeolites with short microporous channels offer advantages in the diffusion of guest molecules, leading to significant improvements in their adsorption and catalytic performance, as well as a reduction in coke formation during catalytic reactions. However, preparing zeolite L (LTL) with an ultrashort length (20–50 nm) along the c-axis has proven challenging due to its preferential growth behavior along the one-dimensional microporous channel direction. Additionally, the conventional synthesis method of zeolite L struggles to achieve both low aspect ratio and short length along the c-axis due to the coupling of nucleation and growth stages during crystallization. In this study, we present an innovative approach by utilizing seeds of nanorod-cluster zeolite L, pre-prepared under high alkalinity conditions, to synthesize a novel morphology of zeolite L mesocrystals. The resulting zeolite L product exhibits a unique cluster structure composed of a series of disc nanocrystals with an ultrashort c-axis length (approximately 29 nm), and the entire crystallization process is completed within just 4 h in a low alkaline system without the need for additional additives. This intentionally designed seed-induced synthesis method effectively decouples the nucleation and growth stages of zeolite L, enabling precise control of each stage to achieve the desired morphology. By analyzing the time-resolved evolution of mesoscopic nuclei and microscopic building units in the synthetic system, we find that the ring-cage structures dissolved from seeds exist as four-membered rings and eight-membered rings. These structures accelerate gel ordering and shorten the induction period. Meanwhile, the reserved part of the seeds provides densely-distributed nuclei for growth, resulting in the formation of the novel disc-cluster structures. Furthermore, by controlling growth conditions, we confirm the assembly of worm-like precursor particles during the growth period, allowing for precise regulation of the length along the c-axis of each disc within the range of 18 to 55 nm. Moreover, we extensively demonstrate the significantly enhanced adsorption and diffusion properties of zeolite L with an ultrashort c-axis for a range of model molecules, spanning sizes from 0.43 to 4.5 nm, in both gaseous and liquid phase systems. Our typical sample exhibits advantages in the diffusion rate of small molecules and the adsorption capacity of large molecules in the gaseous phase. It holds great potential for practical applications in the adsorption and separation of aromatic hydrocarbons, as well as the adsorption of dyes and proteins.

Key words: Zeolite L, Crystallization mechanism, Nonclassical crystallization, Morphology regulation, Adsorption performance, Seed-assisted synthesis