Macrocyclic Hosts for Sequestering PFAS Anions
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Solution Overview
Problem
Current technologies lack effective methods for sequestering nonspherical anions, particularly sulfonates and carboxylates, which are components of persistent and toxic PFAS compounds, due to their weak binding affinities and environmental persistence.
Innovation Solution
Development of macrocyclic moieties with electropositive E-H bond donors, such as aromatic, amine, amide, urea, or thiourea groups, that form chelates with anions, specifically designed to bind non-spherical and large anions like sulfonates and carboxylates, which are immobilized or incorporated into polymers for enhanced affinity and sequestration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hosts are designed to bind spherical anions through C-H hydrogen bonding, then binding affinity can be achieved (Ka>10^6 M^-1), but the ability to bind nonspherical anions remains insufficient
Solution Approach 1:
The patent introduces electron-withdrawing groups at specific positions on the aromatic rings of the macrocyclic host, creating localized regions of enhanced electropositivity on C-H bonds. This local modification allows the host to form stronger C-H···anion hydrogen bonds while maintaining the overall macrocyclic structure, thereby achieving both high binding affinity and improved capability to bind nonspherical anions like sulfonates and carboxylates
Solution Approach 2:
The patent systematically varies the position and number of electron-withdrawing groups (such as fluorine atoms) on the aromatic rings to optimize the electropositivity of C-H bonds. By changing these molecular parameters, the host achieves enhanced binding affinity for both spherical and nonspherical anions, resolving the contradiction between binding strength and anion shape adaptability
2Ease of manufacture
If conventional methods are used for PFAS removal, then treatment can be performed, but effective sequestration of sulfonates and carboxylates is not achieved due to weak binding affinities
Solution Approach 1:
The patent modifies the molecular parameters of the host by incorporating electron-withdrawing groups that enhance the electropositivity of C-H bonds. This parameter change transforms the host's binding capability, enabling it to effectively sequester sulfonates and carboxylates (the anionic heads of PFAS) through strong C-H···anion hydrogen bonds, thereby achieving reliable PFAS removal while maintaining treatment feasibility
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
The macrocyclic moieties exhibit high affinity for nonspherical anions, effectively sequestering PFAS compounds, demonstrating strong binding constants and potential for use in filtering membranes that can repeatedly remove PFAS from aqueous systems, achieving concentrations below regulatory limits.
Implementation Method 1
The macrocyclic moiety includes groups including an electropositive E-H bond donor extending into a cavity of the macrocyclic moiety wherein E is selected from the group consisting of C, N, and O, and wherein two or more groups including an electropositive E-H donor interacting with an anion to form a chelate with the anion
Implementation Method 2
two or more groups including an electropositive E-H donor interacting with an anion to form a chelate with the anion
Data Source
AI summary
A method of sequestering anions from a liquid including the anions includes contacting a composition comprising at least one macrocyclic moiety with the liquid. The macrocyclic moiety includes groups including an electropositive E-H bond donor extending into a cavity of the macrocyclic moiety wherein E is selected from the group consisting of C, N, and O, wherein two or more groups including an electropositive E-H donor interact with an anion to form a chelate with the anion.