Abstract

Mechanochemistry, which induces chemical reactions via mechanical agitation, offers a promising alternative to traditional solution-based synthesis by reducing solvent use and chemical waste. This thesis investigates mechanochemistry-specific methods for the sustainable and scalable synthesis of small molecules and functional materials.
Chapter 2 employs resonant acoustic mixing (RAM) to perform mechanoredox diazonium couplings, with BaTiO3 as the piezoelectric catalyst. RAM proceeds without formal grinding or impact media and is readily scalable compared to ball-milling. X-ray diffraction and spectroscopy indicate that reusability of BaTiO3 as a mechanoredox catalyst under ball-milling or RAM is limited by boration.
Chapter 3 introduces the concept of direct mechanoredox catalysis by utilizing a piezoelectric organic polymer, polyvinylidene difluoride (PVDF). PVDF, transformed into a piezoelectric phase, is used to create catalytically active reaction vessels, coatings, and inserts, enabling mechanoredox reactions under ball-mill and RAM conditions. Using aryldiazonium salt borylation as a testbed, five methods for PVDF-based catalysis are explored: (i) PVDF as a powder additive, (ii) a milling jar, (iii) a coating on conventional jars, and a strip insert under (iv) ball-milling or (v) RAM conditions.
Chapter 4 demonstrates a rapid, room-temperature mechanochemical synthesis of 2 and 3 dimensional boroxine covalent organic frameworks (COFs), enabled by using trimethylboroxine as a dehydrating reagent to overcome the hydrolytic sensitivity of boroxine based COFs. This approach achieves high-porosity, crystalline COF, including the first 3-D COF synthesized mechanochemically. Compared to solvothermal methods, this method reduces solvent consumption 20-fold and reaction time 100-fold, delivering quantitative yields with minimal workup. Straightforward scale-up by RAM enables synthesis of multi-gram amounts of the target COFs.
Chapter 5 investigates RAM-assisted topochemical [2+2] photocycloaddition reactions of trans 1,2 bis(4 pyridyl)ethylene to synthesize cyclobutane moieties in the solid state. Appending ultraviolet light-emitting diodes to the RAM instrument enables templated cocrystallization and photocycloaddition to proceed in situ in one pot. This study specifically reports the supramolecular catalysis potential of four templates, including citric acid. Notably, we show that the reaction works when using lemon juice as catalyst, thus elevating the green chemistry aspects of the methodology.
Collectively, this thesis advances mechanochemistry methods and demonstrates potential for sustainable and scalable synthesis.