(668f) Gas Adsorption Properties of NH2-MIL-53(Al) Metal Organic Framework: Experimental and Modeling Insights

Gas adsorption properties of NH₂-MIL-53(Al)
metal organic framework: Experimental and modeling insights

Mudit Baurai, Prudhviraj Medikonda, Prashant
Mishra, Satyannarayana Edubilli, Sasidhar
Gumma^*

Department
of Chemical Engineering, Indian Institute of Technology Guwahati

Guwahati
- 781039, Assam, India.

Corresponding author’s email:  s.gumma@iitg.ac.in (S. Gumma)

During the past two decades, Metal
Organic frameworks (MOFs) has gained much research attention
in the field of gas adsorption/separation due to their fascinating
characteristics like high and selective adsorption capacity, tunable pore
structure and ease of post synthetic modification towards specific applications.

MIL
(Material Institut Lavoisier) series of MOFs were
extensively studied for gas separation applications. Among these materials,
MIL-53(Al), which exhibits structural transformation form lp (large pore) domain to np (narrow pore) domain and vice versa
(so-called breathing phenomenon) upon adsorption of certain guest molecules
(like CO₂, CH₄etc), by
changing temperature or by applying mechanical pressure was interesting and
studied by many researchers. The amine functionalized form of this MOF i.e. NH₂-MIL-53(Al)
also shows a similar behavior. However, there are certain differences in the
nature such as after activation at room temperature MIL-53(Al) exhibits large
pore (lp)
form, whereas NH₂-MIL-53(Al) show a very narrow pore (vnp) form due to
the hydrogen bonding between NH₂ group, oxygen atoms and OH group of
the framework. Interestingly, higher value of CO₂ capacity and
selectivity are reported on NH₂-MIL-53(Al) for sub-atmospheric
pressure. However, to the best of our knowledge, a detailed adsorption study
including several adsorbates (covering a wide range of polarity and polarizability), high pressure and multiple temperatures
seems to be unavailable in the literature. Hence, in this work, we measured pure
gas adsorption properties of CO₂, CH₄, N₂ and
CO on NH₂-MIL-53(Al) at three different temperatures viz. 293, 318 and 354 K over a pressure
ranging 0 ─ 100 bar. In addition, attempts are made to relate the
physical properties of gases with the structural transformation of NH₂-MIL-53(Al).

Key
words

Adsorption,
Metal organic frameworks (MOFs), flexible MOFs, Gas separation