In industrial production, harmful gases act like imperceptible undercurrents, constantly threatening production safety, product quality, and the ecological environment. Whether it’s benzene compounds in chemical plants or hydrogen sulfide in wastewater treatment facilities, accurately and efficiently removing these specific threats from complex mixed gas flows has always been a key challenge in the field of industrial gas purification.
Now, a revolutionary material is moving from the laboratory to the threshold of industrial applications. Like a “smart lock” crafted by molecular engineering, it can “tailor-make” adsorption pores for specific harmful gas molecules. This is the metal-organic framework (MOF) material.
The Disruptive Principle of MOFs:
Metal-organic frameworks (MOFs) are three-dimensional network structure crystalline materials formed by the self-assembly of metal ions or clusters with organic ligands. Its core appeal lies in its extreme designability—scientists can precisely control the pore size, shape, and internal chemical environment of materials, much like building blocks, by altering the types and connections of the metal center and organic ligands.
This enables MOFs to achieve “selective adsorption,” a feat unattainable by traditional materials. The principle is primarily based on two mechanisms:
- 1.Size sieving effect : When the pore size of MOFs is designed between the target molecule and other molecules, it acts like a molecular-level sieve. For example, researchers in Munich designed a MOF material whose pores allow benzene molecules to enter while completely blocking slightly largercyclohexane molecules, achieving near-absolute separation.
- 2. Chemical recognition effect : By “decorating” the inner walls of the pores with specific functional groups, MOFs can generate specific interactions with target gas molecules. For example, pores rich in aromatic rings can strongly capture benzene molecules through interactions; introducing basic sites such as amine groups (-NH₂) can efficiently adsorb acidic hydrogen sulfide gas through acid-base interactions.
How MOFs Precisely Combat Benzene and Hydrogen Sulfide
For Benzene Compounds: Benzene, toluene, xylene, and other benzene compounds are typical industrial VOCs with high toxicity. MOF solutions demonstrate the ability to address these issues in stages:
Deep Trace Removal: In chemical production, removing trace benzene impurities (down to 1000 ppm) from cyclohexane products is an industry challenge. Research shows that certain MOF materials exhibit extremely high selectivity for this, capable of purifying cyclohexane with a purity higher than 99.999% from a 1:20 benzene/cyclohexane mixture.
Addressing High-Concentration Leaks: Responding to sudden leaks requires materials with high adsorption capacity. A novel aluminum-based mesoporous MOF material ,with its large pore volume, achieves a benzene saturation adsorption capacity of 11.37 mmol/g, and has low heat of adsorption, meaning lower energy consumption for subsequent desorption and regeneration.
For Hydrogen Sulfide: Hydrogen sulfide (H₂S) is highly corrosive and toxic. While standalone MOFs sometimes have limited adsorption capacity, the “MOFs+” composite strategy has opened up new avenues. Studies have confirmed that loading the amine-rich polymer polyethyleneimine (PEI) into the pores of MOFs (such as ZIF-8) can significantly enhance the capture capacity of H₂S. This is equivalent to placing more “grip” capable of chemically binding with H₂S within the “room” of the molecular sieve, increasing the adsorption capacity by tens of times.
Prospects and Challenges of MOF Filter Media
Despite its promising prospects, the large-scale industrial application of MOF filter media still faces several core challenges:
Cost and Scale Production: The metals and ligands used in some MOFs are expensive, necessitating the development of cheaper and more sustainable synthesis routes.
Long-Term Stability and Cyclicability:In real-world industrial waste gases characterized by high temperature, high humidity, or complex impurities (such as organosilicon, NOx, etc.), the chemical and mechanical stability of the MOF structure is crucial. The material must be able to withstand multiple adsorption-desorption regeneration cycles.
Standardization and System Design: Standardizing and modularizing MOF filter media and integrating them into existing purification systems requires close collaboration between materials scientists and industrial engineers.
As an expert in HEPA /ULPA for industrial air purification, Trenntech is closely monitoring this materials revolution. We believe that next-generation industrial filter media incorporating MOF precision adsorption technology will not only significantly improve production safety and environmental standards but also provide a key technology for the green transformation of global industry by reducing energy consumption and operating costs.