- Elucidating gating effects for hydrogen sorption in MFU-4-type triazolate-based metal-organic frameworks featuring different pore sizes
-
A highly porous member of isoreticular MFU-4-type frameworks, [Zn 5Cl4(BTDD)3] (MFU-4l(arge)) (H 2-BTDD=bis(1H-1,2,3-triazolo[4,5-b],[4′,5′-i])dibenzo[1, 4]dioxin), has been synthesized using ZnCl2 and H2-BTDD in N,N-dimethylformamide as a solvent. MFU-4l represents the first example of MFU-4-type frameworks featuring large pore apertures of 9.1a A Here, MFU-4l serves as a reference compound to evaluate the origin of unique and specific gas-sorption properties of MFU-4, reported previously. The latter framework features narrow-sized pores of 2.5a A that allow passage of sufficiently small molecules only (such as hydrogen or water), whereas molecules with larger kinetic diameters (e.g., argon or nitrogen) are excluded from uptake. The crystal structure of MFU-4l has been solved ab initio by direct methods from 3D electron-diffraction data acquired from a single nanosized crystal through automated electron diffraction tomography (ADT) in combination with electron-beam precession. Independently, it has been solved using powder X-ray diffraction. Thermogravimetric analysis (TGA) and variable-temperature X-ray powder diffraction (XRPD) experiments carried out on MFU-4l indicate that it is stable up to 500°C (N2 atmosphere) and up to 350°C in air. The framework adsorbs 4a wt% hydrogen at 20a bar and 77a K, which is twice the amount compared to MFU-4. The isosteric heat of adsorption starts for low surface coverage at 5a kJmol-1 and decreases to 3.5a kJmol -1 at higher H2 uptake. In contrast, MFU-4 possesses a nearly constant isosteric heat of adsorption of ca. 7a kJmol-1 over a wide range of surface coverage. Moreover, MFU-4 exhibits a H2 desorption maximum at 71a K, which is the highest temperature ever measured for hydrogen physisorbed on metal-organic frameworks (MOFs).
- Denysenko, Dmytro,Grzywa, MacIej,Tonigold, Markus,Streppel, Barbara,Krkljus, Ivana,Hirscher, Michael,Mugnaioli, Enrico,Kolb, Ute,Hanss, Jan,Volkmer, Dirk
-
-
Read Online
- Designing Open Metal Sites in Metal-Organic Frameworks for Paraffin/Olefin Separations
-
Incorporating open metal sites (OMS) into metal-organic frameworks allows design of well-defined binding sites for selective molecular adsorption, which has a profound impact on catalysis and separations. We demonstrate that Cu(I) sites incorporated into MFU-4l preferentially adsorb olefins over paraffins. Density functional theory (DFT) calculations show that the OMS are independent, with no dependence of binding energy on olefin loading up to one olefin per Cu(I). Experimentally, increasing Cu(I) loading increased olefin uptake without affecting the binding energy, as predicted by DFT and confirmed by temperature-programmed desorption. The potential of this material for olefin/paraffin separation under ambient conditions was investigated by gas adsorption and column breakthrough experiments for an equimolar ratio of olefin/paraffin. High-grade propylene and ethylene (>99.999%) can be generated using temperature-concentration swing recycling from a Cu(I)-MFU-4l packed column with no measurable paraffin breakthrough.
- Mohamed, Mona H.,Yang, Yahui,Li, Lin,Zhang, Sen,Ruffley, Jonathan P.,Jarvi, Austin Gamble,Saxena, Sunil,Veser, G?tz,Johnson, J. Karl,Rosi, Nathaniel L.
-
-
Read Online
- Insights into Catalytic Hydrolysis of Organophosphonates at M-OH Sites of Azolate-Based Metal Organic Frameworks
-
Organophosphorus nerve agents, a class of extremely toxic chemical warfare agents (CWAs), have remained a threat to humanity because of their continued use against civilian populations. To date, Zr(IV)-based metal organic framework (MOFs) are the most pre
- Cao, Ran,Chen, Haoyuan,Farha, Omar K.,Islamoglu, Timur,Kirlikovali, Kent O.,Mian, Mohammad Rasel,Snurr, Randall Q.
-
supporting information
p. 9893 - 9900
(2021/07/19)
-