Insights into the temperature-dependent "breathing" of a flexible fluorinated metal-organic framework.
The framework expansion and contraction upon carbon dioxide uptake was studied in a partially fluorinated metal-organic framework, FMOF-2. The results show framework expansion and contraction (breathing) as a function of pressure and temperature. Even at temperatures as low as -30 °C, two phase transitions seem to take place with a pressure step (corresponding to the second transition) that is greatly dependent on temperature. This behavior is described by the model proposed by Coudert and co-workers showing that the material seems to undergo two phase transitions that are temperature-dependent. The isosteric heats of adsorption at high pressures show a minimum that is concurrent with the region of CO(2)  loadings where the second pressure step occurs. It was deduced that these lower enthalpy values are a consequence of the energy cost related to the expansion or reopening of the framework. Lastly, the large and reversible breathing behavior may be a product of the combination of the high elasticity of zinc (II) coordination and the apparent high flexibility of the V-shaped organic building block.
Pacific Northwest National Laboratory, 902 N Battelle Blvd., Richland, WA 99352, USA. carlos.fernandez@pnnl.gov
Carlos A
CA
Fernandez
Praveen K
PK
Thallapally
B Peter
BP
McGrail
D000327:Adsorption; D002245:Carbon Dioxide / Q000737:chemistry; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D011312:Pressure; D013499:Surface Properties; D013696:Temperature
D009942:Organometallic Compounds; D002245:Carbon Dioxide