Sustainable supercritical-mechanochemical process.

Area of Science:

• Materials Science
• Chemical Engineering
• Green Chemistry

Background:

• Mechanochemistry enables direct conversion of metal oxides to metal-organic frameworks (MOFs), maximizing atom utilization.
• Conventional MOF synthesis often relies on energy-intensive and solvent-heavy methods.

Purpose of the Study:

• To develop an integrated, quasi-continuous synthesis, separation, and activation process for MOFs using mechanochemistry in a supercritical regime.
• To enhance the efficiency and scalability of MOF production through a novel supercritical-mechanochemical (SCM) approach.

Main Methods:

• Utilized supercritical CO2 (SC CO2) to facilitate uniform cosolvent distribution and optimize mass transfer in mechanochemical hot-spots.
• Employed SC CO2-cosolvent circulation to promote the formation of specific topological frameworks from metastable phases.
• Implemented a pilot-scale facility for quasi-continuous MOF production, incorporating separation and activation steps.

Main Results:

• Achieved a rapid production rate of 544.29 kg·m⁻³·d⁻¹ in an 8-hour process cycle.
• Demonstrated high recovery rates for ligand (42.66 wt%) and cosolvent (89.48 wt%).
• Verified substantial cost advantages compared to conventional solvent-based MOF synthesis methods.

Conclusions:

• The supercritical-mechanochemical (SCM) process offers a sustainable and cost-effective alternative for scalable MOF production.
• SCM enhances MOF synthesis by improving mass transfer, accelerating nucleation, and enabling the formation of specific framework topologies.
• The integrated nature of SCM, combining synthesis, separation, and activation, presents a significant advancement in MOF manufacturing.