摘要
Hierarchical porous zeolitic imidazolate frameworks （ZIFs） have potential for adsorption, catalysis and chemical sensing applications. Ultrafast synthesis of ZIFs at room temperature and pressure is particularly desirable for large-scale industrial production. Here, we developed a green and versatile method using organic amines as supramolecular templates （organic amine-template） to rapidly synthesize hierarchical porous ZIFs （ZIF-8, ZIF-61 and ZIF-90） at room temperature and pressure. The synthesis time was reduced dramatically to within 1 min, and the resulting ZIFs had multimodal hierarchical porous structures with mesopores/ macropores interconnected with micropores. Notably, the space-time yield （STY） of hierarchical porous ZIF-8 was up to 1.29×10^4 kg m^-3 d^-1, which is more than three times higher than that reported using other methods. Furthermore, the morphologies and porosities of the produced ZIFs could be readily tuned by controlling the synthesis time or type of organic amine. The organic amine played two roles in the synthesis： （1） a protonation agent to deprotonate organic ligands, facilitating the formation of ZIF crystals, and （2） an structure directing agent to direct mesopore/macropore formation. The resulting hierarchical porous ZIF-8 exhibited enhanced uptake capacities and diffusion rates for guest molecules relative to its microporous counterpart. This work provides a new direction for the green and efficient synthesis of various hierarchical porous ZIFs with high STYs for a wide range of applications.
在常温下快速合成具有多级孔结构的ZIFs村料具有重要的意义:一方面,多级孔道结构能有效地增加分子扩散速率、降低其传质阻力,这对于涉及大分子参与的反应具有重要意义,扩大了村料的应用范围;另一方面,在常温下快速合成ZIFs村料不仅能大幅降低能源消耗,并且能极大地提高生产效率,是一种绿色高效的工艺路线.本文采用有机胺类作为模板,首次在常温下快速合成具有高空时产率的3种多级ZIFs村料(ZIF-8,ZIF-61以及ZIF-90),村料的合成时缩短至1分钟,同时兼具微孔、介孔、大孔结构.此外,ZIFs产物的形貌和多孔性质可以通过调节胺模板的类型或者合成时间来调控.更为重要的是,ZIFs村料的空时产率高达1.29×10~4 kg m^(-3)d^(-1),比之前报导过的值高出3倍,这为ZIFs村料的商业化生产提供了可能.最后,我们通过对有机胺类分子进行计算机模拟,再结合之前文献报导的结果,得到了一般性的合成机理:一方面有机胺作为质子化剂使得有机配体去质子化,被质子化的配体迅速地和金属离子结合形成金属有机骨架;另一方面,有机胺作为模板被用来引导介孔和大孔结构的形成.
基金
supported by the National Natural Science Foundation of China (21576094)
SRFDP (20130172110012)
the Fundamental Research Funds for the Central Universities (2015ZM046)
作者简介
Chongxiong Duan is a Ph.D candidate at South China University of Technology （SCUT）, under the supervision of Prof. Hongxia Xi. His research focused on the synthesis of hierarchical porous nanomaterials.;Corresponding authors： （emails： chemlic@scut.edu.cn （Li C）;Chao Li received his BSc, MSc and PhD degrees in chemical engineering from Northwest University in 2007, Central South University in 2010, and SCUT in 2016, respectively. During 2012-2014, he worked as a visiting scholar at the Department of Chemical Engineering, the University of Massachusetts-Amherst, USA. In 2016, he joined SCUT as a postdoc member. His research interests include synthesis and characterization of functional nanoporous materials （zeolite, MOF, silica, carbon）, heterogeneous catalysis and green chemistry.;Corresponding authors： （emails： cehxxi@scut.edu.cn （Xi H））Hongxia Xi received her PhD degree in Chemical Engineering from SCUT in 1996. She then worked as a post-doctor for two years at Sun Yat-sen Unviersity, as a visiting scholar for one year at Savoie University, France, and as a senior visiting scholar for six months at The State University of New Jersey, USA. She is currently a professor of chemical engineering at SCUT. Her research interests focus on the development of porous materials and their application.
