COF-432 Imine Framework for Low-Temperature Water Harvesting
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Solution Overview
Problem
Current materials for water harvesting from air lack hydrolytic stability, exhibit hysteretic behavior, and require high regeneration temperatures, limiting their efficiency and long-term cycling performance.
Innovation Solution
Development of a highly crystalline covalent organic framework, COF-432, with a unique imine-linked, two-dimensional structure that exhibits an 'S'-shaped water sorption isotherm without hysteresis, allowing for efficient water uptake and release at low relative humidity and low regeneration temperatures, along with charged COFs that enhance water uptake capacity and rate at low and medium relative humidity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional materials are used for water harvesting from air, then water uptake capacity may be achieved, but hydrolytic stability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by introducing hydrolytically stable imine linkages and specific topological structures (sql, hcb, kgm, fxt, kgd, bex) into the COF framework. This structural parameter change enables the material to maintain both high water uptake capacity and exceptional hydrolytic stability, resolving the contradiction between quantity of substance absorbed and compositional stability.
Solution Approach 2:
The patent creates composite COF materials combining specific organic building blocks with stable imine linkages and defined topologies. This composite structure integrates multiple functional elements (porous framework, imine linkages, topological arrangements) to achieve both high water sorption capacity and resistance to hydrolysis, simultaneously satisfying both requirements.
2Quantity of substance
If conventional COFs are used for water sorption, then water uptake may be achieved, but hysteretic behavior increases
Solution Approach 1:
The patent changes the structural parameters by adopting specific topologies (sql, hcb, kgm, fxt, kgd, bex) and imine-linked frameworks that enable reversible sorption behavior. This parameter change eliminates hysteresis by creating a highly crystalline structure with uniform pore pathways, allowing water to be taken up and released without hysteretic losses, thus improving reliability while maintaining water uptake capacity.
3Quantity of substance
If conventional materials are used for water harvesting, then water can be captured, but regeneration temperature increases
Solution Approach 1:
The patent changes the thermal parameters by designing COFs with imine linkages and specific topologies that create favorable thermodynamics for water sorption. This structural parameter change results in low isosteric heat of adsorption (̃48 kJ mol−1), enabling regeneration at ultra-low temperatures while maintaining high water capture capacity, thus resolving the contradiction between water capture and regeneration energy requirements.
4Quantity of substance
If conventional COFs are used for cycling applications, then initial water sorption may be achieved, but cycling stability deteriorates
Solution Approach 1:
The patent changes the structural and compositional parameters by creating highly crystalline COFs with imine linkages and defined topologies that are inherently resistant to degradation. This parameter change enables the material to maintain its working capacity (0.23 g gCOF−1) and crystallinity through 300+ water sorption-desorption cycles, achieving both initial performance and long-term cycling stability simultaneously.
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
COF-432 demonstrates exceptional hydrolytic stability, minimal hysteresis, and low regeneration energy, while charged COFs increase water uptake capacity and rate, making them suitable for efficient water harvesting and simultaneous CO2 capture from air and flue gas.
Implementation Method 1
COF-432 is a porous, crystalline two-dimensional imine-linked COF with a voided square grid topology... exhibits an 'S'-shaped water sorption isotherm with a steep pore-filling step at low relative humidity
Implementation Method 2
the combination is tetratopic and tritopic linkers... the linkage is imine (—CH═N—)... the composition is constructed from tetratopic 1,1,2,2-tetrakis(4-aminophenyl)ethene [ETTA, C26H16(NH2)4] and tritopic 1,3,5-triformylbenzene [TFB, C6H3(CHO)3], termed COF-432 {[(ETTA)3(TFB)4]imine}
Data Source
AI summary
Chemically and thermally stable covalent organic framework (COF) materials are configured and operative as solid adsorbents for capturing gases and water.