Fabrication of 2-D and 3-D ZIF Based Structured Adsorbents for Carbon Capture

Abstract

With the alarming increase in the CO2 emissions worldwide, urgent actions are required
in order to tackle and minimize the detrimental impacts of global warming and climate
change.
In order to make a contribution in this direction, this master’s thesis focuses on the fabrication
of zeolitic imidazolate framework (ZIF) based structured adsorbents using low-cost
2-D and 3-D supports of different nature. ZIFs are a subclass of MOFs (metal organic
frameworks), which present exceptional thermal and chemical stability along with large
pore volume and surface area. In order to fully exploit their potential as adsorbents or
catalysts, structuring of these porous powders into hierarchically porous structures are
of great interest. Therefore, with that intention in mind, coating of two different ZIFs
such as ZIF-8 and ZIF-67 onto different types of metallic and non-metallic substrates was
investigated.
Among the different synthesis routes explored, mechanically stable ZIF coating was achieved
with blade coating method for 2-D substrates, especially over non-metallic substrates such
as glass fiber, cardboard and silicone rubber. Hot pressing method (HoP) presented a
solvent- and binder-free approach, yet pretreatment of the metallic surface is required to
achieve a stable ZIF growth. In case of 3-D substrates i.e. melamine sponge, results revealed
that a low-cost 3-D structured adsorbent with high loading of ZIFs (100 mg/cm3)
can be achieved via in-situ direct growth approach by placing the sponge horizontally in
the synthesis vial using water as solvent.
Having optimized the process of fabricating ZIF-loaded melamine sponges, their performances
in terms of capturing CO2 were investigated via dynamic breakthrough experiments.
A gas mixture of CO2 – N2 (20% - 80% vol.) was employed for these separation
experiments. The results demonstrated that ZIF-67 was a more effienct adsorbent in comparison
to ZIF-8, demonstrating an eight-fold increase in the adsorption capacity for CO2
capture. Finally, post-synthesis modification on ZIF-8 was performed in an attempt to
improve its low adsorption capacity.
Overall, the present study provides an alternative, facile, economical, energy-efficient and
environment-friendly path to obtain MOF based composites in 2-D and 3-D structure,
including a proof of concept in adsorption and separation applications.

Date of Award	2021
Original language	English
Supervisor	Joeri Denayer (Promotor)