Date of Award

6-2025

Degree Name

MS in Civil and Environmental Engineering

Department/Program

Civil and Environmental Engineering

College

College of Engineering

Advisor

Amro El Badawy

Advisor Department

Civil and Environmental Engineering

Advisor College

College of Engineering

Abstract

The primary driver of climate change is the release of carbon dioxide (CO2) from fossil fuel combustion. Global climate change has resulted in sea level rise, adverse weather patterns, and countless other negative global effects. Several carbon-reduction frameworks emphasize the transition to clean energy sources; however, other strategies must be concurrently pursued to immediately and effectively reduce atmospheric carbon dioxide point source emissions. Metal organic frameworks (MOFs) are a promising new technology for post-combustion carbon dioxide capture. The materials are synthesized using organic linker molecules and metal ion joints. Notably, there are several challenges with various types of MOFs (e.g., low CO2 selectivity, low structural integrity, and the use of toxic solvents for synthesis of MOFs) that must be overcome to enable their large-scale applications under real-world conditions. The literature has documented post-synthesis modifications to MOFs aimed at addressing the mentioned issues. Nevertheless, this field of research is in its early stages, and further investigations are needed to enhance the optimization of MOFs for efficient CO2 capture. UTSA-280 is a promising new calcium-based, eco-friendly, and structurally resilient MOF. There are few preliminary studies on the carbon sorption capabilities of USTA-280; however, initial findings have yielded favorable results. A previous study, conducted through Cal Poly, showed that USTA-280 sorbed carbon dioxide when functionalized with an anime-based polymer, polyethyleneimine (PEI). Specifically, the study discovered the functionalization of USTA-280 with 600 MW polyethyleneimine produced the highest carbon sorption when compared to functionalization of USTA-280 with varying polyethyleneimine molecular weights and arrangements. Thus, the objective of this research study was to functionalize USTA-280 with 600 MW polyethyleneimine (PEI), with different percent weight DI:PEI solutions to find the optimal PEI loading percentage that enhances the sorption capacity and selectively for CO2. To explore the sorption capabilities of USTA-280 with other carbon-selective polymers, USTA-280 was also modified with Tetraethylenepentamine and linear PEI. It was hypothesized that the incorporation of carbon selective polymers into the pores of USTA-280 MOFs would: 1) introduce Lewis basic amine groups that selectively sorb CO2 molecules and 2) the carbon selective polymers molecules would narrow the pores of the USTA-280 to an optimal size that enables physical attraction between the CO2 molecules and the surfaces of the MOFs. USTA-280 MOFs were synthesized and functionalized with 600 MW PEI in the following PEI to DI percent weight solutions: 0.7%, 1.2%, and 1.5%. Furthermore, USTA-280 MOFs were functionalized with 1.5% polymer to DI percent weight with TEPA and linear PEI. The CO2 sorption capacity of the USTA-280 MOFs were quantified at CO2 pressures ranging from 0.03 – 1.0 atm using a quartz crystal microbalance (QCM) assembly. Modifications of the USTA-280 MOFs with PEI and TEPA enhanced their CO2 sorption capacity and the impact of percent weight of the functionalization solution on this sorption capacity was analyzed. The 1.5% bPEI modified USTA-280 exhibited the highest sorption (1.58 mmol/g average sorption and 2.7 mmol/g peak sorption) of the tested and previously recorded PEI-USTA-280 combinations. The functionalization methods explored in the given study for linear PEI impregnation did not yield carbon sorption onto the USTA-280. Furthermore, the produced USTA-280 was characterized using x-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Moving forward, it is essential to undertake future research to explore the selectivity of the USTA-280 MOFs examined in this study and to devise a cost-effective approach for regenerating the used MOFs.

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