Multivariate Hydrogen-Bonded Organic Frameworks for Optimum Atmospheric Water Harvesting

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Chemical Engineering

Background:

• Hydrogen-bonded organic frameworks (HOFs) are promising for water adsorption but often lack performance for atmospheric water harvesting (AWH).
• Monotonic building units in HOFs limit their ability to meet diverse AWH demands.
• Tuning framework properties is crucial for developing efficient water harvesting materials.

Purpose of the Study:

• To develop a multivariate (MTV) strategy for tuning HOF properties for enhanced atmospheric water harvesting (AWH).
• To investigate the impact of incorporating amino groups into HOFs on water adsorption and stability.
• To demonstrate programmable performance in soft porous crystals through precise functionalization.

Main Methods:

• Synthesis of parent HOF (PFC-76) using [1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (TPTCA) linkers.
• Functionalization of TPTCA with amino groups in controlled ratios (50%, 67%, 80%) to create multivariate HOFs.
• Single-crystal X-ray crystallography to analyze framework structure, dynamics, and water arrangement during adsorption.

Main Results:

• Introduction of amino groups modulated framework packing and dynamic behavior, leading to sliding dynamics in PFC-76-NH2.
• Systematic variation of amino content maintained crystallinity and porosity while creating an atactic distribution of functional groups.
• Enhanced H2O uptake, optimized adsorption onset, and superior cycling stability were achieved in the functionalized HOFs.

Conclusions:

• The multivariate strategy effectively tunes HOFs for improved atmospheric water harvesting (AWH) performance.
• Precise control over functional group incorporation and framework dynamics enables programmable material properties.
• This approach offers a pathway for designing advanced soft porous crystals for practical water management applications.