UCLA

The shale gas revolution has boosted the United States economy ever since the early 2000s. Its surge in shale gas production has led to an abundance of the light alkanes including methane (CH4), ethane (C2H6), and propane (C3H8), presenting both opportunities and challenges in terms of their conversion into valuable products.CH4 is the primary component of shale gas. Its emission is indeed driving global climate change. Developing an efficient chemical transformation pathway for CH4 provides an applicable solution to use CH4 in shale gas and meanwhile reduce its emission into atmosphere, yet it is still one of the remaining ‘grand challenges’ in chemistry, especially for the one that occurs at ambient conditions. The key resides on the discovery of new catalytic systems to break the very strong C-H bond within a CH4 molecule. The major part of this dissertation focuses on the development of metal complexes as the homogeneous electrocatalysts by which the injected CH4 can be directly converted into functionalized product in liquid phase. At a relatively “wild” guess from the classic hard-soft acid-base (HSAB) theory, we speculated that a high-valent transition metal, divalent silver (AgII) radical, as a soft class (b) Lewis acid based on Pearson’s classification, is a suitable candidate for CH4 activation due to methyl (CH3) moiety’s relatively low value of chemical hardness. Inspired by such notion, we reported that electrochemically generated AgII readily functionalizes CH4 into methyl bisulfate (CH3OSO3H) as a precursor of methanol (CH3OH) at ambient conditions in concentrated sulfuric acid (98% H2SO4). The second work further provides chemical insight that metal-bound bisulfate ligand (–OSO3H) introduced by 98% H2SO4 could be redox-active toward CH4 with our reported molecular catalyst vanadium (V)-oxo dimer (V2V,V). While CH4 is often used for energy production, the extraction and utilization of other non-negligible components including C2H6 has diversified the applications and markets for shale gas products. To expand our knowledge base in the emerging field of electrocatalytic alkane functionalization, we further discovered and developed the direct electrochemical coupling of C2H6 at ambient conditions, where all of the gas products can be easily separated from the cheap and green aqueous electrolytes and transported to the downstream chemical production. This work also highlights electrolyte engineering to avoid the common use of 98% H2SO4 electrolyte, which may inspire environmentally benign electrocatalysis for alkane activation. Altogether, these three independent works show the full potential of electrocatalytic ambient light alkane functionalization for shale gas utilization on the chemical industry in the near future. Throughout my time as a graduate student, with the understanding of scientific knowledge, technological applications, and practical tasks, I have demonstrated how the combination of electrochemistry, radical chemistry, organometallics, and homogeneous catalysis with instrumentation skills can provide fresh perspectives on fundamental chemistry and chemical engineering. The use of electrogenerated radicals to C-H activation is a distinctive phenomenon, offering a direct way to overcome kinetic inertness and facilitate innovative reactivity pathways of small molecules.