Difference Between Zeolite and MOF

The key difference between zeolite and MOF is that zeolite is mainly useful as a catalyst, whereas MOF is ideal for support structures for catalysis or can act as a catalyst.

We can identify zeolite and metal organic frameworks or MOFs as two common porous material having pores less than 1 nanometers (as in zeolite) or larger than 1 nanometer (as in MOFs), respectively.

CONTENTS

1. Overview and Key Difference
2. What is Zeolite 
3. What is MOF
4. Zeolite and MOF  in Tabular Form
5. Summary – Zeolite vs MOF

What is Zeolite?

Zeolite is a microporous aluminosilicate mineral. It is mainly useful as a catalyst. On a commercial scale, it is useful as an adsorbent. This term came into fame in 1756 after the research of Swedish mineralogist Axel Fredrik Cronstedt. He observed the production of large amounts of steam from water (which occurs inside the material through adsorption) upon rapid heating of a particular material containing stilbite. Depending on this observation, this scientist named this material zeolite, which has the Greek meaning, “zeo” =”to boil”, and “lithos”=”stone”.

Zeolite Structure

There is a porous structure in zeolite that can associate with a wide variety of cations, including Na+, K+, Ca2+ and Mg2+. These are positively charged ions that can be loosely held. Therefore, these ions can be readily exchanged for other ions upon contact with a solution. The mineral members in the zeolite group include analcime, chabazite, clinoptilolite, stilbite, etc.

When considering the properties of zeolite, the naturally occurring forms can react with alkaline groundwater. Moreover, these materials can get crystallized in post-depositional environments over a large period of time. Furthermore, the natural zeolite forms rarely occur in the pure state. They are usually contaminated with other minerals, metals, quartz, etc.

What is MOF?

Metal-organic frameworks or MOFs are hybrid porous materials consisting of both organic and inorganic groups. We can observe the structure of these materials as crystalline and 3D in nature, and it can utilize a combination of rigid inorganic groups such as metal ions or metallic clusters along with flexible organic linker ligands. This use of both rigid and flexible groups can enable the MOFs to get long-range tunable pores, which can associate with a wide range of molecules. This material can undergo tunning, which allows them to be selective for the type of molecules that can enter into their pores.

MOF Structure

When considering the structure of the MOFs closely, we can observe the inorganic and organic groups are arranged in a specific way making the pores. The structure of MOFs occurs as a coordination network of inorganic nodes. These nodes tend to form the corners of these pores providing, geometrical stability along with structural regularity. Moreover, the organic linkers that are connecting the nodes together provide synthetic versatility and modular functionality. Furthermore, we can see the same structure is repeated in the 3D structure of MOFs.

What is the Difference Between Zeolite and MOF?

Although zeolite was the option as a porous material for many years, the development of other materials such as metal-organic frameworks (MOF) and covalent organic frameworks (COF) has challenged its use at present. The key difference between zeolite and MOF is that zeolite is mainly useful as a catalyst whereas MOF is ideal for support structures for catalysis, or they can act as catalysts themselves. Moreover, the pores in zeolite are less than 1 nanometer, whereas the pores in MOF are larger than 1 nanometer.

The following infographic summarizes the difference between zeolite and MOF in tabular form.

Summary – Zeolite vs MOF

We can identify zeolite and metal organic frameworks or MOFs as two common porous material having pores less than 1 nanometers (as in zeolite) or larger than 1 nanometer (as in MOFs), respectively. The key difference between zeolite and MOF is that zeolite is mainly useful as a catalyst whereas MOF is ideal for support structures for catalysis or they can act as catalysts themselves.

Reference:

1. Critchley, Liam. “A Guide to the Difference Between MOFs (Metal-Organic Frameworks) and COFs (Covalent Organic Frameworks).” AZoNano.com, 16 Nov. 2018.

Image Courtesy:

1. “Thomsonite-61017” By Rob Lavinsky, iRocks.com – (CC-BY-SA-3.0) via Commons Wikimedia
2. “Zeolite structure as an assembly of tetrahedra” By François-Xavier Coudert – Own work (CC BY 4.0) via Commons Wikimedia