Design and synthesis of metal-organic frameworks :Doctor of Philosophy - Major: Chemical Engineering

Dissertation for the Degree of Doctor of Philosophy

Design and Synthesis of Metal-Organic Frameworks

for CO, CO2, and C7H8 Adsorption

Le Van Nhieu

Department of Chemical Engineering

Graduate School

Kyung Hee University

Seoul, Korea

June, 2021

Design and Synthesis of Metal-Organic Frameworks

for CO, CO2, and C7H8 Adsorption

Le Van Nhieu

Department of Chemical Engineering

Graduate School

Kyung Hee University

Seoul, Korea

June, 2021

Design and Synthesis of Metal-Organic Frameworks

for CO, CO2, and C7H8 Adsorption

by

Le Van Nhieu

Advised by

Prof. Jinsoo Kim

Submitted to the Department of Chemical Engineering

and the Faculty of the Gradual School of

Kyung Hee University in partial fulfillment

of the requirement for degree of

Doctor of Philosophy

Dissertation Committee

Chairman Prof. Eun Yeol Lee

Prof. Bum Jun Park

Prof. Chang Kyoo Yoo

Prof. Kye Sang Yoo

Prof. Jinsoo Kim

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ABSTRACT

Design and Synthesis of Metal-Organic Frameworks for CO, CO2, and C7H8

Adsorption

Le Van Nhieu

Department of Chemical Engineering

Graduate School of Kyung Hee University

Seoul, Korea

To date, gas adsorption has attracted attention in the context of more serious air

pollution as a result of industrialization and the growing population. By the way, the gaseous

contaminants are effectively managed to contribute to the improvement of air quality,

simultaneously, supply several important chemicals (CO, CO2) used as raw materials for the

industrial manufacturing process. And, the derived-adsorbents from metal organic

frameworks (MOFs) have gradually become a key contributor to the amelioration of gas

adsorption performance.

The separation of CO out of gas mixture, especially containing CO2 is an important

mission in the industrial production sector but encounter huge challenges due to the higher

polarizability of CO2 than that of CO. Most of the investigation showed that after introducing

Cu(I) into pore system of MOF-support, the resulting materials exhibited a higher adsorption

capacity of CO than CO2 whereas a contrary result was observed on the original MOFs. This

is due to -complexation formed between Cu(I) and CO species. Among the reported MOFs,

MIL-100(Fe) possesses high BET surface area, thermal stability ( ̴ 320 oC), and tunability

of the oxidation state of iron ions (Fe(II) and Fe(III)) under high temperature (150 ̴ 250 oC).

So, a simple route is employed to introduce Cu(I) on MIL-100(Fe), in which Cu(II) is

directly transferred to Cu(I) thanks to Fe(II), but no requirement support from reducing

agents. However, MIL-100(Fe) is typically synthesized in closed batch systems, which is

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not favorable for large-scale production. Herein, we report a scalable MOF synthesis route

based on a continuous flow tubular reactor equipped with microwave volumetric heating.

The system enabled continuous crystallization of MIL-100(Fe) with a high space-time yield

of ~771.6 kg m-3

day-1

under relatively mild conditions in a range of temperature (100 ̴ 110

oC) and resident time of 50 min. The product quality is evaluated via porous property and

crystallinity in comparison to the traditional method. Ultimately, the MIL-100(Fe) was used

as a support to prepare Cu(I)-modified π complexation adsorbents. The adsorbents exhibited

preferred CO adsorption over CO2, and the adsorption performance was confronted to, or

even higher than most of the Cu(I)-modified π complexation adsorbents in previous reports.

Until now, the CO-selective adsorbents are kept developing towards the improvement

of CO uptake capacity and CO/CO2 selectivity, but Cu(I)-incorporated MOFs are instability

in the air. This is the main reason for reducing CO separation performance in the real gas

environment being usually available a certain amount of oxygen and moisture. Recently,

some reports have revealed a strategy to improve the stability of Cu(I)-incorporated MOFs,

however, their CO adsorption capacity is modest. Therefore, The development of a CO￾selective adsorbent with large CO adsorption capacity, high CO/CO2 selectivity, and good

stability is still a huge challenge. In this dissertation, a novel Cu(I)-incorporated MIL-100(Fe)

adsorbent for CO/CO2 separation is prepared using a host–guest redox strategy by

combining the co-addition of Zn(II) and Cu(II) inside the MIL-100(Fe)’s pore system. The

addition of Zn(II) resulted in a higher Cu(I) yield of the adsorbent due to the facilitated

regeneration of Fe(II), which was utilized for the reduction of Cu(II). Therefore, both CO

uptake amount and achieved CO/CO2 selectivity on Cu(I)Zn@MIL-100(Fe) with only 10

wt% of Zn loading were considerably higher than that of the benchmark Cu(I)-incorporated

adsorbents. In addition, the presence of the Zn(II) in Cu(I)Zn@MIL-100(Fe)-10 improved

the oxygen resistance. This study opens a new perspective for developing efficient CO￾selective π-complexation adsorbents with high CO/CO2 selectivity and superior oxygen

resistance.

Unlike CO adsorption, the MOF-adsorbent for capturing the target gas like CO2 or