In the field of materials chemistry, organic framework materials (OFMs) — a family of porous crystalline or polymeric materials — have gained remarkable attention for their structural tunability, large surface areas, and wide range of applications.

These frameworks are typically composed of organic linkers and molecular nodes connected through coordination, covalent, or hydrogen bonding interactions, forming extended networks with controllable porosity.

The major types of organic frameworks include: Metal–Organic Frameworks (MOFs), Covalent Organic Frameworks (COFs), Hydrogen-Bonded Organic Frameworks (HOFs), Halogen-Bonded Organic Frameworks (XOFs) and Porous Organic Frameworks (POFs).

Each category has distinct bonding mechanisms and application advantages.

1. Metal–Organic Frameworks (MOFs)

What are MOFs?

Metal–Organic Frameworks (MOFs) are crystalline materials constructed from metal ions or clusters coordinated with organic ligands, such as carboxylates, pyridines or imidazoles.

This modular molecular building block approach enables precise control over pore size, topology and chemical functionality.

Examples:

• MOF-5: Zn²⁺ + terephthalic acid
• HKUST-1: Cu²⁺ + trimesic acid
• UiO-66: Zr⁴⁺ + terephthalic acid

Key Features:

• Exceptionally high surface area (up to thousands of m²/g)
• Tunable porosity (micro- to mesoporous)
• Adjustable chemical environment via ligand modification

Applications:

• Gas storage and separation (CO₂, H₂, CH₄)
• Catalysis and photocatalysis
• Drug delivery and controlled release
• MOF-derived carbons or oxides for energy storage

Trend Insight:

Next-generation Zr-, Fe- and Cr-based MOFs exhibit enhanced stability and scalability, bridging the gap between lab research and industrial use.

2. Covalent Organic Frameworks (COFs)

What are COFs?

Covalent Organic Frameworks (COFs) are fully organic crystalline materials formed via strong covalent bonds (C–N, B–O, C=C, etc.) without metal centers. They combine low density, high stability, and structural precision, making them ideal for functional materials design.

Examples:

• COF-1, COF-5 (B–O linked 2D aromatic frameworks)
• TpPa family (C–N linked hydrazone-based COFs)

Key Features:

• Entirely organic, π-conjugated architectures
• High chemical and thermal stability
• Precisely tunable pore sizes and surface functionalities

Applications:

• Photocatalysis and optoelectronic materials
• CO₂ capture and selective adsorption
• Chemical sensing and gas detection
• Energy storage and conversion (e.g., Li-ion batteries)

Research Focus:

COFs are evolving from 2D layered frameworks to 3D architectures, enabling multifunctional applications in semiconductors and catalysis.

3. Hydrogen-Bonded Organic Frameworks (HOFs)

What are HOFs?

Hydrogen-bonded Organic Frameworks (HOFs) are supramolecular networks formed through directional hydrogen bonds between organic molecules without metals or strong covalent linkages.

While the hydrogen bonds are weaker, the overall structure can be stabilized by multiple cooperative interactions.

Examples:

• HOF-1: composed of tetra(benzomelamine)methane as the basic unit through hydrogen bonding
• HOF-FJU-1: A representative with excellent stability, stabilized through multiple hydrogen bonds and π-π stacking interactions, suitable for hydrocarbon separation.
• HOF-TCBPA: composed of tetra(4-carboxyphenyl)pyrazine, exhibiting dynamic responsiveness and fluorescence properties.

Key Attributes:

• Mild synthesis conditions; self-assembly in solution
• Reversible and reconfigurable frameworks
• High structural flexibility and dynamic behavior

Applications:

• Gas adsorption and molecular separation
• Luminescent sensing and fluorescence detection
• Responsive materials for stimuli-triggered functions

Emerging Area:

HOFs represent a “soft porous network” concept, bridging the rigidity of MOFs/COFs and the dynamic adaptability of supramolecular systems.

4. Halogen-Bonded Organic Frameworks (XOFs)

What are XOFs?

Halogen-Bonded Organic Frameworks (XOFs) are crystalline porous materials formed by the self-assembly of organic building blocks through halogen bonds, a type of noncovalent interaction analogous to hydrogen bonding. The halogen bond (X···Y) arises between a halogen atom (X = I, Br, Cl) with an electrophilic σ-hole and a Lewis base (Y = N, O, S, or π-system).

Key Characteristics:

• Directional and highly selective self-assembly
• Tunable bond strength via choice of halogen donor/acceptor
• Crystalline porous networks with defined channels or cavities
• Often compatible with other weak interactions (π–π stacking, hydrogen bonding)

Advantages:

• Enables precise crystal engineering without metal ions
• Offers controllable molecular recognition and guest inclusion properties
• Provides new strategies for functional porous materials with halogen-based reactivity

Applications:

• Molecular recognition and separation
• Gas adsorption and storage
• Optical, electronic, and sensing materials

Outlook:

XOFs combine directional supramolecular design with the versatility of organic synthesis, opening new avenues in nonmetallic crystalline porous materials.

5. Porous Organic Frameworks (POFs)

What are POFs?

Porous Organic Frameworks (POFs) sometimes called Porous Organic Polymers (POPs) are amorphous or semi-ordered polymers featuring intrinsic microporosity. They are synthesized through polymerization reactions of organic monomers via C–C or C–N bond formation.

Types:

• CMPs (Conjugated Microporous Polymers)
• PIMs (Polymers of Intrinsic Microporosity)
• POPs (Porous Organic Polymers)

Key Features:

• High chemical and thermal stability
• Scalable, solution-processable synthesis
• Flexible functionalization with catalytic or adsorptive groups

Applications:

• Gas adsorption and CO₂ capture
• Organic pollutant removal
• Catalysis and separation membranes
• Electrodes for energy storage devices

Comparison of Major Organic Frameworks

Future Outlook

The evolution of organic framework materials is moving toward:

• Green and solvent-free synthesis routes

• Hybrid frameworks combining multiple interactions (e.g., H-bond + X-bond)

• Functional integration for multi-responsive or conductive frameworks

• Scalable production bridging lab research and industrial deployment

Organic frameworks are becoming core materials in carbon capture, catalysis, and energy storage, linking molecular design with real-world performance.

J&K Scientific – Your Partner in Framework Material Research

At J&K Scientific, we support researchers and industrial partners in developing MOF, COF, HOF, XOF and POF materials through high-purity reagents and synthesis intermediates.

Our portfolio:

• Metal salts (Zn, Cu, Zr, Fe, Al)

• Organic linkers (terephthalic acid, trimesic acid, imidazole derivatives)

• Monomers for covalent and halogen-bonded frameworks

• Solvents and modulators for green or solvothermal synthesis