Creating hierarchical pores in metal–organic frameworks via postsynthetic reactions

• Published in: Nature protocols Vol. 18; no. 2; pp. 604 - 625
• Main Authors: Wang, Kun-Yu, Yang, Zhentao, Zhang, Jiaqi, Banerjee, Sayan, Joseph, Elizabeth A., Hsu, Yu-Chuan, Yuan, Shuai, Feng, Liang, Zhou, Hong-Cai
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.02.2023; Nature Publishing Group
• Subjects: 639/638/298/921; 639/638/549; Analytical Chemistry; Biological Techniques; Biomedical and Life Sciences; Catalysts; Computational Biology/Bioinformatics; Drug Carriers; Drug delivery; Hydrolysis; Life Sciences; Metal-Organic Frameworks; Metals; Microarrays; Organic Chemistry; Pore size; Pores; Porosity; Porous materials; Protocol; Washing
• ISSN: 1754-2189; 1750-2799
• DOI: 10.1038/s41596-022-00759-7

Metal–organic frameworks (MOFs) demonstrate promise for a multitude of applications owing to their high porosity and surface area. However, the majority of conventional MOFs possess only micropores with very limited accessibility to substances larger than 2 nm—especially functional biomacromolecules like some proteins. It is challenging to create an appropriately large pore size while avoiding framework collapse in MOFs. Herein, we present the generation of mesopores in microporous MOFs through three facile and effective techniques, namely Soxhlet washing, linker hydrolysis and linker thermolysis. These postsynthetic elimination approaches have been applied in selected MOFs, including PCN-250, PCN-160 and UiO-66, and controllably generate MOFs with hierarchical pores and high stability. Our work demonstrates reproducible and straightforward methods resulting in hierarchically porous materials that possess the benefits of mesoporosity while borrowing the robustness of a micropore framework. All the procedures can be conducted reliably at a multigram scale and operation time less than 6 h, representing a significant effort in the field of MOF synthesis. These hierarchically porous MOFs show great promise in a wide range of applications as efficient adsorbents, catalysts and drug carriers. Many applications of metal–organic frameworks relate to their nanometer-sized pores. This protocol describes three postsynthetic methods for making metal–organic frameworks with multiple levels of pores: Soxhlet washing, linker hydrolysis and linker thermolysis.