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Nanoporous Asymmetric Poly(Ionic Liquid) Membrane

Periodic Reporting for period 4 - NAPOLI (Nanoporous Asymmetric Poly(Ionic Liquid) Membrane)

Reporting period: 2019-07-01 to 2021-07-31

The NAPOLI project studies a previously unknown class of polymer membranes that carry simultaneously three unique features, i.e. ionic charges, a property gradient and a nanoporous state. Such membranes are missing in the field and we aim at their novel synthesis, structure-property relationship, and broad materials applications so to actively complement the state-of-the-art membrane technology.

With the rapid growth of population on earth, there will be a huge demand for enough energy and clean environment. The current status of energy and environmental technology will not meet that need. Membrane technology is one of the key battlefields that can mitigate such issues. Broadening the structure scope of membranes, expanding their application spectrum, and understand physics and chemistry occurring in innovative membranes are necessarily needed and encouraged. The NAPOLI project will bring new knowledge and technology to the membrane field.

The project has overall four objectives: 1) produce a library of NAPOLI membranes previously inaccessible in a large scale and size, 2) to understand their structure-property relationship, which will serve as a roadmap to guide this field, 3) explore applications beyond filtration membranes, especially in the environment (sensors, sorbent, etc.) and energy (ion separation, desalination, etc.) areas. 4) to train young researchers in EU to approach the frontiers of the state-of-the-art membrane science and technology.

As a conclusion, the action ends up successfully with a comprehensive knowledge gained on this type of new membrane systems. With such knowledge, the NAPOLI membrane will enter a technology development period, where follow-up work will realize their practical use.
As an overview, the NAPOLI project has significantly expanded the synthetic toolbox of such previously unattainable membranes that simultaneously bear nanopores, ionic charges and a gradient property profile. The synthetic advance enables comprehensive studies of properties and (multi)functions of NAPOLI membranes. Numerous applications have been found, some of which are far beyond what we originally expected. We also successfully addressed the mechanical/chemical stability and sustainability issues of the NAPOLI membranes, a crucial step for their future commercialization.

Exploitation: 1). twos patents. One patent in switchable oil/water filtration system, and one patent in anti-corona virus coatings have been filed. 2) A new research grant. On the way to exploration of possible applications, we produced porous carbon membranes from NAPOLI membranes and received a new grant from Knut&Alice Wallenberg foundation to investigate porous carbon membranes.. 3) Education of young PhD students and postdocs. Four of them have already grown into Full Professors by the time of this report. 4) Attract excellent young researchers. For example, in 2016, Dr. Jian-Ke Sun joined my ERC team as a prestigious Alexander von Humboldt Postdoc Fellow.

Dissemination: 1) National and international conferences. The outcome of this project has been presented by me and the ERC team in ca. 30 conferences and workshops. 2) Publication in journals with open access. In the entire project period. There have been 73 project publications in peer-reviewed journals. 3) Website. We use our group website (www.yuan-group.com) as the website hub of the ERC project to present research advance. 4) Social media. We used social media and scientific platforms to broadcast our research results. For example, we used the X-MOL platform and Wiley Materialsview science channels.

Performed work is listed beneath.
1) The team has fully understood the formation mechanism of the NAPOLI membranes. This mechanism has not been so clear to us before this project. This mechanistic understanding significantly expands the structure library of NAPOLI membranes, and it has inspired us next to discover several other novel synthetic methods towards NAPOI membranes.

2) A big pool of different NAPOLI structures has further enabled us a systematic investigation of a variety of experimental parameters, so we successfully improved the structural stability and sustainability of such membranes. Via optimization and new synthetic tools, the cost in membrane fabrication on a large size has been massively reduced.

3) Along the rapid synthetic progress, we have pushed forward the technological use of such membranes, from the initial detection of organic molecules to the sensing of toxic gas, the weak acids, and H2O2. Our recent breakthrough is to use NAPOLI membranes as template to fabricate nanoporous metal organic framework/poly(ionic liquid) hybrid membranes and porous nitrogen-doped carbon membranes, which have tremendous potential in electrocatalysis and sensing.

4) With collaborators together, we have deepened our understanding of physics and chemistry of poly(ionic liquid)s and their membranes. For example, the ion conduction, mass flow, their interaction with CO2, the effect of cation structures on their interaction with metal ions, etc. This knowledge sets a firm base for the next stage investigation of poly(ionic liquid)s and their NAPOLI membranes.
In the synthetic area, the project has massively broadened the synthetic tools. We first applied the same method to synthesize both polymer to organic-inorganic hybrid membranes. Then, we developed new methodologies. To highlight, we used COOH-functionalized graphene oxide to replace poly(acrylic acid) for better nanofiltration membranes, and used a single poly(ionic liquid) to prepare porous membranes.
To bring NAPOLI membranes from fundamental research to industrial utilization, the stability (chemical and mechanical) and the sustainability aspects must be addressed. We first introduced covalent crosslinks into the membrane to improve chemical stability. To improve the mechanical performance, we used a filter paper as a substrate and then developed a new method to produce flexible porous membranes. To improve the sustainability, we optimized the synthesis of poly(ionic liquid) in one-step in an aqueous media. IN addition, we developed fully recyclable NAPOLI membranes.

As emerging applications, in the 4th reporting period, we succeeded in using NAPOLI membranes as sacrificial template to prepare nitrogen-doped porous carbon membranes of high conductivity, very promising in electrode applications of various devices. As for the sensing application, by coating a silica needle with NAPOLI membranes, we significantly enhance the headspace solid phase microextraction efficiency to detect various vapor organic compounds (VOCs). We also further functionalized the NAPOLI membranes with metal (Cu, Au and Ag) nanoparticles that are of catalytic function. Such membranes showed catalytic activities in degradation of p-nitrophenol, an industrial waste in water.
This SEM image of NAPOLI membrane is used as postcard for Max Planck Institute of Colloids&Interface