Inorganic Chemistry Seminar – Jiahong Li, Graduate Student

About the event

Title: Carboxylate-based Metal–organic Frameworks: Solvent-free Synthesis, Thermodynamic Analysis, and Catalytic Activity

Abstract: Metal–organic frameworks (MOFs) are a class of coordination polymers assembled from metal clusters and organic linkers, which possess high-level structural and functional tunability. Such tunability allows the design of countless possible framework structures, which continues to find their applications in catalysis, gas/small molecule separations, drug delivery, and energy storage. Conventionally, MOFs are synthesized via solvothermal/hydrothermal methods, which often require a large amount of organic solvent and toxic reagents and sometimes yield inconsistent products from batch to batch. Therefore, it is imperative to provide innovative synthetic solutions to address these challenges and keep up with industrial processes. Firstly, we developed a phase-selective, solvent-free, green synthetic method for the aluminum trimesates (Al-BTCs) system, which generates three distinct phases, MIL-96, MIL-100, and MIL-110, from the identical metal and ligand precursors. It remains a challenge to obtain the pure-phase product, and the co-occurrence of the MIL-96 and MIL-100 phases is often observed during the synthesis. A set of calorimetric and in-situ X-ray diffraction experiments were dedicated to investigating the energetic perspective of the formation of Al-BTCs. Our results show that the linker stabilization of the Al-polyhedra plays an important role in the formation of the Al-BTC frameworks, and the higher coordinative metal-polyhedra attains more enthalpic stabilization from the coordinated ligands. Secondly, a large-scale modulator-free synthetic approach was utilized to produce functionalized hierarchically porous UiO-66 (HP-UiO-66) type material. Defect sites, mesopores, and different ratios of mixed ligands were introduced to enhance the catalytic activity of HP-UiO-66s. Finally, CO₂ cycloaddition into organic epoxide was selected as the model reaction to probe the catalytic performances of seven X:Y-HP-UiO-66 (X:Y= molar ratio of NH₂BDC : BDC) derivatives with different acid-base functionalities, and the excellent catalytic results provide a promising insight of rational design of MOFs via fine-tunning of functionality for more effective catalytic applications.