Synthesis, Characterization, and Utilization of Metal-Organic Frameworks (MOFs) and Their Pyrolyzed Functional Carbons

Structural modulation of metal-organic frameworks (MOFs) is of importance because it can be used to enhance the gas adsorption abilities and heterogeneous catalytic performance of MOFs and their pyrolyzed analogues. Therefore, the ultimate goal achieved in this dissertation is to 1) synthesize novel MOFs and 2) tailor/modify the structure of the MOFs prior to pyrolysis, thereby directing/controlling the properties of the resulting functional carbons.

Zn-based MOFs (Zn-MOFs) with free pyridine functionalities are promising materials but the synthesis of these MOFs is difficult due to the tendency of the pyridine N to coordinate with the Zn centers. This dissertation documents synthetic efforts for the generation of free pyridine-incorporating Zn-MOFs and their characterizations. In addition to the syntheses of novel Zn-MOFs, the incorporation of pyridines in these Zn-MOFs motivates their use as templates pyrolyzed to produce N-doped carbons. This dissertation, hence, covers the generation of N-doped carbons derived from these Zn-MOF templates. Furthermore, the structures of these Zn-MOFs were modulated to enhance the CO₂ uptake in the pyrolyzed Zn-MOF analogues.

Additionally, the pyrolysis of desired metal-incorporating MOF templates to produce metal-supported on carbons was studied. Specifically, structural tuning of these MOFs can be accomplished through post-synthetic modification (PSM). PSM has been validated as an excellent synthetic route for site-isolating target metal species into the MOFs’ structures via coordination. Ultimately, these metal-modified IRMOF-3 templates were synthesized and pyrolyzed to produce novel carbon catalysts. Four transition metals (i.e., Ru, W, V, and Ti) are used in this study since these metals are reported as active sites for converting biomass derivatives. The modified IRMOF-3 intermediates and their pyrolyzed counterparts were characterized and used as catalysts for catalytic transformation of biomass derivatives. Furthermore, the Ti-supported carbon was also employed as a catalyst in the oxidation of dibenzothiophene.

In addition, the pyrolysis of active V species-incorporating MIL-47 (V) template is envisioned to produce carbon-supported V catalysts. This was motivated by our previous studies about the use of pyrolyzed MIL-125 (Ti) analogues as catalysts for oxidizing dibenzothiophene. Specifically, MIL-47 (V) was pyrolyzed at different pyrolysis temperatures and the resulting V catalysts were tested in this reaction.