In this study, a porous Ni-MOF formulated as {(H 2 NMe 2 )[Ni 3 (μ 3 OH)(TPT)(TZB) 3 ](H 2 O) 6 (DMA) 7 } n (TZB = 4-(1H-tetrazol-5-yl)benzoate, TPT = 2,4,6-tri(4-pyridyl)-1,3,5-triazine, and DMA = N,N-dimethylacetamide) was prepared and its C 2 H 2 and CO 2 adsorption performances were systemically studied both experimentally and computationally. The structural analysis by single crystal X-ray diffraction studies reveals that the prepared Ni-MOF crystallizes in the space group P6 3 mc and features a porous pacs -type network composed of trigonal bipyramidal and octahedral cages. The activated Ni-MOF (Ni-MOF-a) shows a high C 2 H 2 uptake capacity of 157 cm 3 /g with a moderate C 2 H 2 /CO 2 IAST selectivity of 3.3 at 298 K and 1 bar. More importantly, Ni-MOF-a shows a low adsorption heat for C 2 H 2 ranging from 24.6 to 27.1 kJ/mol at 298 K with a high separation potential of 2.85 mol/kg. In the computational simulation section, six sets of point charge derived from different approaches (Qeq, Mulliken, PACMOF, mCBAC, Mepoml, PACMAN) and two different force-fields (UFF and Dreiding) were used to calculate the C 2 H 2 and CO 2 adsorption isotherms and then compared with the experimental values. Our results reveal that great care should be taken in the selection of point charges and force fields, and the unsuitable combinations might result in an inappropriate C 2 H 2 /CO 2 selectivity which is against the experimental results.
Mohan Chen,Yichao Wang,Ziwen Fan,Yue Wang,Zheng Niu,Jianping Lang
Graphical We prepared a series of fluorinated MOFs through the post- synthesis modification of the classic Zr-based MOF-808. The fluorinated alkane pores within MOFs can enhance the forces between the framework and C 2 H 2 , therefore, the difference in the adsorption capacity to C 2 H 2 and C 2 H 4 making it possible to effectively separate the C 2 H 2 /C 2 H 4 mixture at room temperature. The separation of ethylene (C 2 H 4 ) and acetylene (C 2 H 2 ) is challenging due to their similar molecular dimensions and boiling points, making conventional methods like cryogenic distillation and solvent extraction inefficient and environmentally harmful. Fluorinated metal-organic frameworks (MOFs) have been proven to be an effective material for the separation of C 2 H 4 and C 2 H 2. However, their direct synthesis is relatively expensive and challenging. In this study, we report a facile post-synthetic modification strategy to introduce fluorinated alkane pores into a zirconium-based MOF, MOF-808. The construction of fluorine-containing pores within the MOFs prefers adsorption for C 2 H 2 attributed to the interaction between the fluorine atoms and C 2 H 2 . This series of fluorinated MOFs demonstrates potential for gas separation processes, with the highest separation ratio reaching 2.67 (1 : 99) at 298 K. Breakthrough experiments for C 2 H 2 /C 2 H 4 mixtures confirmed that fluorinated MOF is capable of separating C 2 H 2 /C 2 H 4 , making it a potential candidate for industrial application. Moreover, the simplicity of the post-synthetic modification method suggests a viable strategy for the synthesis of fluorinated MOFs.
Metal-organic frameworks (MOFs) have emerged as a multi-functional platform for selective gas capture and luminescent detection of harmful pollutants, in which their pore functionality and structural stability are two key factors to be considered for the targeted applications. In this contribution, we present the synthesis and structural evaluation of a new channel-type MOF formulated as {[In 3 (OH) 3 (TATAB) 2 ](DMA) 8 (CH 3 CN) 6 (H 2 O) 2 } n ( 1 , DMA is short for N,N-dimethylacetamide and TATAB is the abbreviation of 4,4′,4″-s-triazine-1,3,5-triyl-p-aminobenzoate) constructed from rod-like [In-(OH)-(COO) 2 ] n chains and the N-rich fluorescent triazine ligand H 3 TATAB. The noninterpenetrated framework of 1 features 1D rhombic channels (13.1 × 14.2 Å 2 ) along the c axis with abundant of free N sites on the pore walls. The solvent-removal framework of 1 ( 1a ) could adsorb large amount of C 2 H 2 (154 cm 3 /g) at 298 K and 1 bar with a moderate C 2 H 2 /CO 2 selectivity (3.7), and its separation performance has been further validated via the break-through experiments. Aqueous-phase sensing experiments demonstrate this MOF exhibits excellent performance of fluorescent detection of 2,4,6-trinitrophenol (TNP) via remarkable fluorescence quenching and obvious blue-shift of maximum emission. In connection to the sensing experiments, we used DFT calculations to reveal the underlying mechanism of such sensing performances via analyzing the energy lever together with electron transfer route.
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