Flexible MOCN Gas Separation Membranes via iPECVD
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Solution Overview
Problem
Current membrane gas separation technologies face challenges in achieving high flux and high gas selectivity, particularly at varying transmembrane pressure differences, and are limited by the brittleness and scalability of ultra-thin gas selective layers, such as porous alumina supported MOF nanosheets and graphene oxides, which are difficult to fabricate in large dimensions and maintain mechanical stability.
Innovation Solution
The development of hyper-thin, flexible metal organic covalent network (MOCN) layers using initiated plasma-enhanced chemical vapor deposition (iPECVD) directly on a membrane support, where zinc tetraphenylporphyrin building units are covalently bonded, enabling efficient gas separation for gas pairs like H2/CH4, H2/N2, O2/N2, and CO2/N2 while maintaining stability across a wide range of pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ultra-thin gas selective layers (MOF nanosheets, graphene oxides) are used to achieve high flux, then gas permeability is improved, but mechanical strength and flexibility deteriorate
Solution Approach 1:
The patent creates a composite structure by covalently bonding porphyrin molecules to form a Metal Organic Covalent Network (MOCN) layer on the membrane support. This composite approach combines the ultra-thin structure needed for high gas flux with the covalent network structure providing mechanical strength and flexibility, resolving the contradiction between thinness and strength.
Solution Approach 2:
The patent develops a flexible thin film MOCN layer that is only a few nanometers thick yet maintains mechanical robustness through covalent bonding. This flexible thin film allows the membrane to operate at high transmembrane pressure differences while maintaining high gas flux, addressing both the productivity improvement and strength preservation needs.
2Manufacturing precision
If controlled oxidative surface modification methods are used to enhance gas selectivity, then gas selectivity is improved, but substrate dependence increases
Solution Approach 1:
The patent develops a universal coating method using initiated PECVD that can be applied to various membrane substrates without requiring substrate-specific optimization. The porphyrin-based MOCN layer forms through a general chemical vapor deposition process that works on different substrate materials, achieving high gas selectivity while maintaining substrate independence and versatility.
Solution Approach 2:
The patent replaces the mechanical/chemical oxidative modification approach with a vapor deposition-based chemical synthesis method. Instead of oxidizing existing surfaces, the porphyrin molecules are deposited and covalently bonded to form the selective layer, creating a substrate-independent process that achieves high gas selectivity through controlled molecular assembly rather than surface chemistry.
3Manufacturing precision
If polymer membrane-supported graphene and GOs films are used to achieve high gas selectivity, then gas selectivity is improved, but gas permeance decreases
Solution Approach 1:
The patent creates a porous MOCN structure through the covalent networking of porphyrin molecules, which forms a controlled porous architecture that allows high gas permeance. The porphyrin-based covalent network maintains open pathways for gas transport while providing molecular-level selectivity, avoiding the dense coating structure that causes permeance loss in polymer-supported graphene systems.
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 MOCN layers demonstrate superior gas selectivities and permeabilities, exceeding industry benchmarks, with enhanced mechanical robustness and scalability, suitable for industrial gas separations, including carbon capture and hydrogen recovery, while maintaining stability under high transmembrane pressure differences.
Implementation Method 1
depositing by iPECVD on a surface of the substrate any one of the polymers described herein
Implementation Method 2
initiated plasma-enhanced chemical vapor deposition (iPECVD)
Implementation Method 3
demonstrate superior gas selectivities and permeabilities, exceeding industry benchmarks
Data Source
AI summary
Described herein are facile, one-step initiated plasma enhanced chemical vapor deposition (iPECVD) methods of synthesizing hyper-thin (e.g., sub-100 nm) and flexible metal organic covalent network (MOCN) layers. As an example, the MOCN may be made from zinc tetraphenylporphyrin (ZnTPP) building units. When deposited on a membrane support, the MOCN layers demonstrate gas separation exceeding the upper bounds for multiple gas pairs while reducing the flux as compared to the support alone.