Non-ambient XRD Investigation of a Hydrophobic Framework Material for Trace CO2 Capture

Metal-organic frameworks (MOFs) are frequently cited as potential materials for efficient gas absorption, filtration and storage. A key parameter for superior storage performance is structural stability under demanding conditions such as elevated temperature, high pressure, or high rela-tive humidity. Non-ambient XRD attachments like the CHC plus+ or chambers of the TTK series from Anton Paar are perfect tools to investigate the structural stability of MOFs under varying environmental conditions.


Employing solids as CO2 capture (C-capture) materials may represent an energy efficient alternative to the traditionally used liquids. However, the challenge of trace level CO2 capture from air under varying conditions (gas composition, humidity level, and temperature) remains.

Materials based on physisorptive CO2 capture have so far proved elusive due to their generally low selectivity for CO2 against atmospheric nitrogen and gaseous H2O. With the rise of metal organic frameworks (MOFs) as an energy efficient solution for trace gas separation, C-capture based on physisorptive materials is once again the focus of extensive research.

The combination of easily adjustable and controllable material properties (e.g. hydrophobicity, pore size, surface charge, etc.) in MOFs, together with the excellent sorption kinetics of physisorbent materials has led to the development of a range of promising new CO2 capture materials with low water affinity. This application report highlights the characterization of one such material, SIFSIX-18-Ni ([Ni(L)2(SiF6)]n, (L = 3,3′,5,5′-tetramethyl-1H,1′H-4,4′-bipyrazole)), by employing Anton Paar non-ambient XRD attachments (TTK and CHC plus+) to study the material under different environmental conditions.1



1. Trace CO2 capture by an ultramicroporous physisorbent with low water affinity, Mukherjee et al., Sci. Adv. 2019; 5 : eaax9171 

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