Sustainable Mechanochemical Synthesis and Manufacturing of Metal-Organic Frameworks for Enhanced Hydrogen Storage

With the increasing severity of greenhouse gas emissions, the need for sustainable and efficient hydrogen storage solutions to replace fossil fuels is becoming increasingly urgent. This thesis investigates sustainable mechanochemical processing routes for metal-organic frameworks (MOFs), focusing on enhancing the hydrogen storage performance of the MOF CuBTC (also known as HKUST-1) through green mechanochemical synthesis, solvent-free mechanochemical modification, and scalable cold-sintering-enabled monolithic moulding technology. The design of Experiments (DoE) methodology was applied to systematically optimise the mechanochemical synthesis of CuBTC, enabling quantitative analysis of the effects of six synthesis parameters on structural and adsorption properties of CuBTC. This optimised CuBTC exhibited a hydrogen uptake of 3.2 wt.% at 20 bar and 77 K, comparable to solvothermally synthesised CuBTC (3.37 wt.%), while maintaining high crystallinity and minimal structural defects. SEM, BET surface area, pore size distribution, and hydrogen adsorption collectively demonstrate that high-quality CuBTC can be produced by ball milling, challenging the widely held assumption that mechanochemical synthesis inevitably leads to defect-rich frameworks. This solvent-free design approach reduces the CuBTC synthesis time to a few minutes while consuming less than 2% of the energy required for conventional solvothermal synthesis. Having established a high-quality, defect-minimised CuBTC via mechanochemical synthesis, the study next extends the application potential of this material through targeted solvent-free mechanochemical modification. Building directly on the optimised CuBTC framework, enhanced hydrogen storage performance was achieved through in situ and post-synthetic incorporation of nickel and magnesium using solvent-free mechanochemical ball milling. This represents the first demonstration of enhanced hydrogen storage performance in a CuBTC by incorporating nickel and magnesium through a combination of in situ and post-modification solvent-free mechanochemical ball milling. By introducing Ni2+ into the CuBTC framework, hydrogen uptake was increased to 4.2 wt.% at 20 bar and 77 K. This represents a 31% improvement over the pristine mechanochemically synthesised CuBTC and 45% higher than previously reported values. These results demonstrate that defect-controlled mechanochemical processing not only preserves, but can further enhance, hydrogen adsorption performance. To transition the synthesis and modification strategies from laboratory to industrial scale, a cold sintering-enabled synthetic manufacturing technique was developed for MOFs pelletisation. Initial application of established cold sintering protocols, involving simultaneous pressing and low-temperature densification, resulted in low product yield and compromised MOF quality, revealing intrinsic incompatibilities between conventional cold sintering and the structural stability of CuBTC. To address this limitation, the manufacturing strategy was redesigned through a sequential one-pot solid-state synthesis followed by cold sintering with controlled methanol soaking. This modified approach decouples MOF formation from densification, enabling simultaneous shaping and consolidation while preserving framework integrity. Under the optimal conditions, methanol soaking for 60 minutes enabled the CuBTC pellets to retain 92.2% of their hydrogen storage capacity (3.54 wt.% H2). This study represents the first systematic investigation of the effect of methanol soaking duration on the structural integrity of CuBTC during cold sintering. Furthermore, the redesigned manufacturing route achieved a twofold increase in product yield compared to mechanochemical ball milling synthesis, highlighting its strong potential for scalable MOF manufacturing with retained hydrogen storage performance. This study provides new, experimentally validated insights into environmentally sustainable, solvent-free synthesis and manufacturing strategies for metal–organic frameworks, and highlights the potential of CuBTC as a high-performance material for hydrogen storage. By integrating synthesis, modification, and scalable shaping within a single processing framework, these findings establish a clear foundation for future advances in MOF design and practical energy storage technologies.<p></p>

Author dc:creator

• Qian Yu (21042023)

• hydrogen storage
• metal-organic frameworks

Statement dc:rights

• All rights reserved
• Open Access after 2026-12-08

Identifier

10779/exe.32582724.v1

OAI identifier oai:identifier

oai:figshare.com:article/32582724