posted on 2023-05-15, 19:05authored byThomas
M. Rayder, Filip Formalik, Simon M. Vornholt, Hilliary Frank, Seryeong Lee, Maytham Alzayer, Zhihengyu Chen, Debabrata Sengupta, Timur Islamoglu, Francesco Paesani, Karena W. Chapman, Randall Q. Snurr, Omar K. Farha
Carbon
capture, storage, and utilization (CCSU) represents an opportunity
to mitigate carbon emissions that drive global anthropogenic climate
change. Promising materials for CCSU through gas adsorption have been
developed by leveraging the porosity, stability, and tunability of
extended crystalline coordination polymers called metal–organic
frameworks (MOFs). While the development of these frameworks has yielded
highly effective CO2 sorbents, an in-depth understanding
of the properties of MOF pores that lead to the most efficient uptake
during sorption would benefit the rational design of more efficient
CCSU materials. Though previous investigations of gas–pore
interactions often assumed that the internal pore environment was
static, discovery of more dynamic behavior represents an opportunity
for precise sorbent engineering. Herein, we report a multifaceted in situ analysis following the adsorption of CO2 in MOF-808 variants with different capping agents (formate, acetate,
and trifluoroacetate: FA, AA, and TFA, respectively). In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)
analysis paired with multivariate analysis tools and in situ powder X-ray diffraction revealed unexpected CO2 interactions
at the node associated with dynamic behavior of node-capping modulators
in the pores of MOF-808, which had previously been assumed to be static.
MOF-808-TFA displays two binding modes, resulting in higher binding
affinity for CO2. Computational analyses further support
these dynamic observations. The beneficial role of these structural
dynamics could play an essential role in building a deeper understanding
of CO2 binding in MOFs.