Gradient Structured Organic Films for Tunable Porosity
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Solution Overview
Problem
Existing methods for fabricating gradient films are sensitive to various factors such as solvent, concentration of reagents, pH, temperature, and additives, and often face issues with compatibility and dissolution of reagents in polar or non-polar systems, leading to suboptimal performance in applications like gas absorption, energy storage, and catalysis.
Innovation Solution
The development of structured organic films (SOFs) with a specific composition that includes segments, linkers, and capping segments, where the segment to capping segment ratio varies across the film's surface, allowing for a controlled gradient in porosity and ionic concentration, thereby enhancing properties such as wettability, charge transport, and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional polymeric membranes are used with pores formed by entanglement of polymer chains, then the membranes are easy to manufacture, but they cannot be easily manipulated into gradient films or films exhibiting porosity gradient across thickness
Solution Approach 1:
The membrane is divided into multiple layers with different porosity characteristics. The electrospun nanofiber layer provides a porous structure, while the COF layer provides a dense separation barrier. This segmentation allows each layer to perform its specific function optimally and enables the formation of gradient structures that traditional homogeneous polymeric membranes cannot achieve.
Solution Approach 2:
The invention uses a composite structure combining electrospun nanofibers (polymer matrix) with covalent organic framework (COF) layers. This composite approach integrates the advantages of both materials: the flexibility and porosity of polymer nanofibers with the ordered pore channels and high selectivity of COFs, enabling gradient film formation while maintaining ease of manufacture.
2Ease of manufacture
If COFs are homogeneously dispersed into polymeric matrices, then the fabrication process is simplified, but voids and COF pore blockage by polymer component occur
Solution Approach 1:
Instead of homogeneous dispersion, the invention segments the membrane into distinct layers: an electrospun nanofiber layer and a COF layer. This segmentation prevents polymer components from blocking COF pores while maintaining fabrication simplicity through sequential layer formation processes.
Solution Approach 2:
The electrospun nanofiber layer acts as a flexible support matrix that allows the COF layer to maintain its ordered pore structure without blockage. The thin film COF layer provides the separation function while the porous nanofiber substrate provides mechanical support and facilitates mass transfer.
3Manufacturing precision
If gradient films are prepared by dissolution and diffusion methods, extrusion, microfluidic techniques, electrochemical techniques or centrifugation, then porosity gradient can be achieved, but sensitivity to solvent, concentration of reagents, pH, temperature and additives increases
Solution Approach 1:
The invention achieves porosity gradient by controlling the concentration and deposition parameters of COF precursors during the layer formation process. By adjusting parameters such as reagent concentration, deposition time, and processing conditions, a controlled gradient in ionic concentration and porosity is achieved without requiring complex equipment or high sensitivity to multiple process variables.
Data Source
AI summary
A structured organic film (SOF) is disclosed. The structured organic film includes a plurality of segments, a plurality of linkers, and a plurality of capping segments. The structured organic film also includes a first surface of the SOF. The film also includes a parallel second surface of the SOF connected to the first surface by a thickness of the SOF, where a segment to capping segment ratio is greater at the first surface as compared to the parallel second surface. A membrane including a free-standing film comprised of a structured organic film is also disclosed.