Development of MOF-5-like ultra-microporous metal-squarate frameworks for efficient acetylene storage and separation

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 11; no. 39; pp. 2123 - 2121
• Main Authors: Li, Hai-Peng, Wang, Jia-Wen, Zhai, Quan-Guo
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 10.10.2023
• Subjects: Acetylene; Adsorption; Aqueous solutions; Flow rates; Hydrogen bonding; Hydrogen bonds; Metal-organic frameworks; Porosity; Separation; Transition metals; Zinc
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d3ta04732f

Although MOF-5 and its related family members are landmark metal-organic frameworks (MOFs), they have large specific surface area and high porosity, which have long been a subject regarding their instability. The introduction of new inorganic building blocks, in addition to classical [Zn 4 O(COO) 6 ], is a promising way to maintain the highly attractive architecture of MOF-5. Herein, a family of new MOF-5-like frameworks were synthesized by using squaric acid (SQ) and transition metal salts, namely, {(NH(CH 3 ) 2 ) 2 [M 4 X 4 (SQ) 3 ]} n (SNNU-505-M, M = Zn, Co and Ni, X = F − and OH − ). In this SNNU-505-M series of compounds, except for the μ 3 -bridging atom of SNNU-505-Zn being an F − ion, all the others are OH − . Compared with MOF-5, SNNU-505-M exhibits good stability in organic solvent and aqueous solutions (pH = 3-13). Furthermore, benefiting from its ultra-micropore size and multiple polarity F − /OH − adsorption sites, SNNU-505-M shows high C 2 H 2 adsorption capacity and excellent separation performance. In particular, SNNU-505-Zn exhibits the best C 2 H 2 /C 2 H 4 (1 : 1) separation performance and its breakthrough interval time is 51 min g −1 at 298 K at a flow rate of 2 mL min −1 . The GCMC calculations further demonstrate that the excellent C 2 H 2 uptake and C 2 H 2 /C 2 H 4 separation performance of SNNU-505-Zn can be mainly attributed to the multiple C-H F hydrogen bonds between the C 2 H 2 molecules and MOF skeleton. A series of ultra-microporous MOF-5-like metal-squarate frameworks exhibit moderate C 2 H 2 uptake capacity, in addition to excellent C 2 H 2 /CO 2 and C 2 H 2 /C 2 H 4 separation ability regulated by strong hydrogen bond interactions.