SYSTEMATIC POSTSYNTHETIC MODIFICATION OF NANOPOROUS ORGANIC FRAMEWORKS AND THEIR PERFORMANCE EVALUATION FOR SELECTIVE CO2 CAPTURE

Author

Timur IslamogluFollow

DOI

https://doi.org/10.25772/M02G-4V82

Defense Date

2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Hani M. El-Kaderi

Abstract

Porous organic polymers (POPs) with high physicochemical stability have attracted significant attention from the scientific community as promising platforms for small gas separation adsorbents. Although POPs have amorphous morphology in general, with the help of organic chemistry toolbox, ultrahigh surface area materials can be synthesized. In particular, nitrogen-rich POPs have been studied intensively due to their enhanced framework-CO₂ interactions. Postsynthetic modification (PSM) of POPs has been instrumental for incorporating different functional groups into the pores of POPs which would increase the CO₂ capture properties. We have shown that functionalizing the surface of POPs with nitro and amine groups increases the CO/N₂ and CO₂/CH₄ selectivity significantly due to selective polarization of CO₂ molecule. In addition, controlled postsynthetic nitration of NPOF-1, a nanoporous organic framework constructed by nickel(0)-catalyzed Yamamoto coupling of 1,3,5-tris(4-bromophenyl)benzene, has been performed and is proven to be a promising route to introduce nitro groups and to convert mesopores to micropores without compromising surface area. Reduction of the nitro groups yields aniline-like amine-functionalized NPOF-1-NH₂. Adequate basicity of the amine functionalities leads to modest isosteric heats of adsorption for CO₂, which allow for high regenerability. The unique combination of high surface area, microporous structure, and amine-functionalized pore walls enables NPOF-1-NH₂ to have remarkable CO₂ working capacity values for removal from landfill gas and flue gas. Benzimidazole-linked polymers have also been shown to have promising CO₂ capture properties. Here, an amine functionalized benzimidazole-linked polymer (BILP-6-NH₂) was synthesized via a combination of pre- and postsynthetic modification techniques in two steps. Experimental studies confirm enhanced CO₂ uptake in BILP-6-NH₂ compared to BILP-6, and DFT calculations were used to understand the interaction modes of CO₂ with BILP-6-NH_2. Using BILP-6-NH_2, higher CO₂ uptake and CO₂/CH₄ selectivity was achieved compared to BILP-6 showing that this material has a very promising working capacity and sorbent selection parameter for landfill gas separation under VSA settings. Additionally, the sorbent evaluation criteria of different classes of organic polymers have been compared in order to reveal structure-property relationships in those materials as solid CO₂ adsorbents.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-13-2016