High-Throughput Direct Synthesis of Cubdc MOF Nanosheets and Their Application in CO2 Separation

Membranes based on metal organic frameworks (MOFs) have attracted increased research attention especially for their application in separation of carbon dioxide^[1,2]. High aspect ratio MOF nanosheets, having thickness on the order of few nanometers and large lateral dimensions are ideal for fabrication of high performing membranes for gas separations.

CuBDC MOF nanosheets first introduced by the Gascon group were synthesized via a gradient synthesis strategy^[3]. They show promising performance in the separation of carbon dioxide from natural gas streams.

In this work, the bottom-up synthesis strategy for CuBDC nanosheets was modified to eliminate the need for gradient synthesis. Instead CuBDC nanosheets were obtained by a direct mixing scheme consisting of homogeneous mixing of the metal and linker solutions. Nanosheets with an average thickness of 30 nm and average lateral dimensions of 2.5 micron were obtained. The aspect ratio of CuBDC nanosheets was optimized by varying parameters such as synthesis time, temperature and concentration of the synthesis solutions. It was found that lower temperature favors higher aspect ratios. The direct synthesis scheme developed herein is advantageous as it is scalable and high-throughput.

Mixed matrix membranes were fabricated by incorporating the CuBDC nanosheets in a polymer matrix and tested for CO₂/N₂ separation performance. A significant increase in the ideal selectivity of CO₂/N₂ was obtained reiterating the promising separation performance of CuBDC nanosheets.

[1] J. E. Bachman, J. R. Long, Energy Environ. Sci 2016, 9, 2031–2036.

[2] Y. Peng, Y. Li, Y. Ban, H. Jin, W. Jiao, X. Liu, W. Yang, Science 2014, 346, 1356–1359.

[3] T. Rodenas, I. Luz, G. Prieto, B. Seoane, H. Miro, A. Corma, F. Kapteijn, F. X. Llabrés i Xamena, J. Gascon, Nat. Mater. 2015, 14, 48–55.