MOF Monoliths via Solvent Drying
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Solution Overview
Problem
Metal-organic frameworks (MOFs) are typically obtained in a powdered crystalline state, making them costly to shape for industrial applications, and the use of binders and high pressure processes reduces their porous properties, leading to low volumetric adsorption capacities and mechanical properties.
Innovation Solution
A method to produce MOF monoliths without binders or high pressures, maintaining the porosity and mechanical properties of MOF single crystals, by mixing MOF precursors in a solvent and drying at ambient conditions, allowing the formation of robust, transparent monolithic structures with high bulk densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MOFs are obtained in powdered crystalline state through conventional synthesis, then the material can be easily synthesized, but the material requires costly shaping processes and binders to achieve suitable forms for industrial applications
Solution Approach 1:
The invention divides the synthesis process into two stages: first synthesizing MOF crystallites in solution, then allowing them to self-assemble into monolithic structures through controlled drying. This segmentation enables the material to form its final shape during synthesis rather than requiring separate shaping operations.
Solution Approach 2:
The invention uses solvent as an intermediary medium that facilitates both the synthesis of MOF crystallites and their subsequent self-assembly into monoliths. The solvent acts as a template and binding medium during the drying process, enabling the formation of robust monolithic structures without requiring additional binders or shaping equipment.
2Shape
If binders and high pressure processes are used to pelletize MOF material, then suitable monolithic structures are formed, but the porous properties are significantly reduced
Solution Approach 1:
The MOF crystallites themselves serve their dual function: they are both the adsorbent material and the structural building blocks. During controlled drying, the crystallites self-assemble into monolithic structures through capillary forces and interparticle interactions, eliminating the need for external binders that would block pores or reduce porosity.
Solution Approach 2:
The invention changes the physical parameters during synthesis - specifically controlling the drying process to transition from a wet slurry to a dry monolith. By controlling humidity, temperature, and drying rate, the system transforms the material's physical state while maintaining pore structure, avoiding the high-pressure conditions that would collapse pores.
3Strength
If high pressure processes are used to create monolithic structures, then the material achieves suitable mechanical properties, but the volumetric adsorption capacities are reduced
Solution Approach 1:
The invention replaces mechanical pressing with a chemical-physical self-assembly process. Instead of applying external high pressure to compact MOF powder, the system uses controlled evaporation of solvent to generate capillary forces that bind crystallites together, forming monoliths with intact pore structures and high volumetric adsorption capacity.
Solution Approach 2:
The invention exploits the phase transition of the solvent from liquid to vapor during controlled drying. This phase transition drives the self-assembly of MOF crystallites into monolithic structures through capillary condensation and evaporation forces, creating strong interparticle bonds without mechanical compression that would damage the porous structure.
4Ease of manufacture
If powdered MOF material is used, then the synthesis is simple, but the volumetric adsorption capacities are low due to interstitial spaces between crystallites
Solution Approach 1:
The invention merges the MOF crystallites into a continuous monolithic structure through controlled self-assembly during drying. This merging eliminates the interstitial spaces between discrete powder particles, increasing the volumetric density of the adsorbent material while maintaining the simplicity of the synthesis process.
Solution Approach 2:
The invention performs the shaping action preliminarily during the synthesis process itself. By controlling the drying conditions during MOF formation, the crystallites self-assemble into monolithic structures before the material is fully formed, eliminating the need for subsequent shaping operations and maximizing volumetric adsorption capacity from the start.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in MOF monoliths with enhanced mechanical properties and volumetric adsorption capacities, retaining the characteristic porosity of MOF single crystals while achieving higher bulk densities, suitable for industrial applications such as gas adsorption and separation.
Implementation Method 1
Metal-organic frameworks (MOFs) are porous crystalline materials prepared by the self-assembly of metal ions and organic ligands
Implementation Method 2
drying at ambient conditions, allowing the formation of robust, transparent monolithic structures
Data Source
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AI summary
Disclosed is a metal-organic framework (MOF) body comprising MOF crystallites adhered to each other via a MOF binder. In one embodiment, the body consists of: MOF crystallites; a MOF binder which binds the crystallites together in the body; optionally, residual solvent; and optionally, one or more additives, wherein the additives are present at a level of not more than 10% by mass. The MOF binder may have substantially the same composition as the MOF crystallites. Alternatively, the MOF binder may have a different composition to the MOF crystallites.