Overcoming the Limitations of Metal-Organic Frameworks with Rational Design and Mechanochemistry

Abstract

Despite their high tunability and porosity, the broader application of MOFs remains restricted due to structural instability, synthetic challenges, and scalability issues. This thesis explores two complementary approaches, rational design and mechanochemistry, to overcome these limitations and expand the functional landscape of MOFs. This thesis is organized in three chapters. Chapter I provides a comprehensive overview of MOFs, focusing on fundamental descriptions of rational design and mechanochemistry. It indicates the challenges associated with framework instability, performance-oriented structural design, and scale-up feasibility, thereby establishing the need for rational and alternative synthesis strategies. Chapter II explores the rational design of MOFs tailored for structural and functional modulation. The first study investigates a Zn-based MOF that exhibits reversible proton conductivity switching in response to humidity. Through coordination environment analysis and activation energy profiling, the threshold behavior is correlated to structural rearrangements upon water sorption. The second study presents a MOF featuring an Olympic ring-like topology, synthesized using symmetrically mismatched ditopic carboxylates. This work illustrates how geometric perturbations in linker design can direct the assembly of topologically complex, unpredictable, structures. Chapter III introduces mechanochemistry as an alternative synthetic route for overcoming synthetic and stability-related limitations in MOFs. In one study, mixed-metal MIL-88 analogues are synthesized via ball milling using pre-designed trimeric clusters. This approach enables isoreticular expansion with enhanced control over metal ratio. Another study demonstrates the reconstruction of decomposed MOFs, such as MOF-5, MOF-177, UiO-67, and ZIF-65, by liquid-assisted grinding. The original crystallinity and porosity of hydrolyzed frameworks are restored without solvothermal processing, suggesting the potential of mechanochemistry for defect healing and sustainable material reuse. Collectively, the findings presented in this thesis illustrate that overcoming the limitations of MOFs requires multiple strategic approaches. Among them, rational design enables precise structural tuning for targeted functionalities, while mechanochemistry provides a scalable and sustainable route to access structures that are otherwise challenging to obtain. These approaches represent viable and forward- looking directions for both the fundamental understanding and practical advancement of this field.