Issue 21, 2018

Environmentally friendly synthesis of flexible MOFs M(NA)2 (M = Zn, Co, Cu, Cd) with large and regenerable ammonia capacity

Abstract

Two environmentally friendly and efficient synthesis methods, NH3-assisted synthesis and solvent-evaporated conversion, have been developed for the synthesis of a series of M(NA)2 (M = Zn, Co, Cu, Cd; NA = nicotinate) flexible MOFs. The two-dimensional M(NA)2 (M = Zn, Co) and three-dimensional M(NA)2 (M = Cu, Cd) materials exhibit peculiar structural transformation. These frameworks can be obtained from dehydration of M(NA)2(H2O)4 (M = Zn, Co, Cu, Cd) which are zero-dimensional supramolecular structures. Interestingly, the structural transformation of M(NA)2 (M = Zn, Co, Cd) is reversible after liquid water adsorption. Due to the flexible structure of these MOFs, they exhibit abnormal NH3 adsorption properties. The two-dimensional Zn(NA)2 shows a gate-opening behavior for NH3 adsorption. Its layers opened at a pressure of 0.22 bar in the first cycle, resulting in a two-step NH3 uptake with a capacity of 10.2 mmol g−1 at 1 bar. The gate-opening pressure shifted to a lower value with cycles. Co(NA)2 has a huge NH3 uptake of 17.5 mmol g−1, which is top-ranking among the reported values. For the NH3 adsorption over Cu(NA)2 and Cd(NA)2, the adsorption rates increase and adsorption equilibrium is achieved faster after three cycles. Their maximum capacity at 1 bar is 13.4 and 6 mmol g−1, respectively. More importantly, all MOFs can be regenerated under vacuum and heating conditions of 150 °C for 70 min, and they all retained the capacity. The advantages of environmentally friendly synthesis, large adsorption capacity, and regenerable properties indicate that M(NA)2 (M = Zn, Co, Cu) are promising candidates for NH3 adsorption.

Graphical abstract: Environmentally friendly synthesis of flexible MOFs M(NA)2 (M = Zn, Co, Cu, Cd) with large and regenerable ammonia capacity

Supplementary files

Article information

Article type
Paper
Submitted
28 Mar 2018
Accepted
25 Apr 2018
First published
25 Apr 2018

J. Mater. Chem. A, 2018,6, 9922-9929

Environmentally friendly synthesis of flexible MOFs M(NA)2 (M = Zn, Co, Cu, Cd) with large and regenerable ammonia capacity

Y. Chen, B. Shan, C. Yang, J. Yang, J. Li and B. Mu, J. Mater. Chem. A, 2018, 6, 9922 DOI: 10.1039/C8TA02845A

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