International research team including Khalifa University paves way towards the design of new simple and efficient photocatalysts made from covalent organic frameworks (COFs) to reduce captured CO2 into useful products

As the world continues to pump carbon into the atmosphere, it is increasingly important to not only reduce emissions but also find ways to capture and use carbon dioxide. Carbon capture and storage technologies are noble approaches, but don’t tend to make much money. Instead, attention turns to economically viable and valuable approaches to turn carbon dioxide into something useful.

Dr. Dinesh Shetty, Assistant Professor of Chemistry, and Dr. Abdul Khayum Mohammed, Postdoctoral Researcher, collaborated with an international team to develop a new photocatalyst to efficiently and sustainably transform carbon dioxide into useful products. The research team comprised members from New York University Abu Dhabi, American University of Beirut, Instituto de Ciencia de Materiales de Madrid, Spain, University of Strasbourg, France, and University of Nova Gorica, Slovenia. The team’s results were published in

“Excessive anthropogenic emissions of carbon dioxide into the atmosphere have led to global warming,” Dr. Shetty explained. “At the same time, CO2 is a nontoxic, inexpensive, abundant, and renewable source of carbon. Converting it into high value-added products would be a viable and economic use of the carbon dioxide around us.”

Numerous processes already exist to transform CO2 emissions into various chemicals valuable for industry, and among these processes, photocatalytic reduction of CO2 has been noted as particularly promising. There’s little wonder why: this is photosynthesis. Green plants convert carbon dioxide and water into carbohydrates, performing this reaction under ambient conditions using just sunlight, which is an inexhaustible and environmentally-friendly energy source. Even better, photocatalytic CO2 reduction doesn’t create any secondary pollution.

“Carbon dioxide can be reduced into many forms, with carbon monoxide and formate the most common reduction products,” Dr. Shetty said. “Formate is preferred as it is the simplest oxygenated species produced, and an intermediate in the formation of methanol and other higher-order hydrocarbons, which can be used in plastics, paints, organic solvents, and fuel cells.”

Photocatalytic reduction of CO2 is not new—many semiconductor and molecular-based systems have been studied. However, their limited conversion efficiency, low binding affinity for CO2, unfavorable active-site architecture, and rapid charge recombination limit their overall performance. Covalent organic frameworks (COFs), such as that developed by the research team, have the potential to address many of these issues.

COFs are a class of materials that form two- or three-dimensional structures through reactions between their organic components, resulting in strong, covalent bonds that create porous, crystalline materials. They are uniquely tunable, with well-defined structures and good chemical stability and plenty of pores for adsorption applications.

Capturing the CO2 is the first step. A sorbent material is needed to selectively grab the carbon dioxide and allow it to collect in the pores in the material. And COFs for CO2 reduction already exist, but the majority produce carbon monoxide as their product, which is the less desirable of the two common products. Those that do produce formate often involve expensive noble metals or even enzymes.

The research team synthesized a novel COF using two different building units known as porphyrins and isoindigo to ensure the captured carbon dioxide reduces into formate, not carbon monoxide. Their PI-COF has a square layered structure and an improved affinity for carbon dioxide adsorption. Even without expensive rare materials or special catalysts, the research team’s PI-COF reduced carbon dioxide into formate with yields comparable to more complex systems.

“Our system performs similarly to others but requires much less power, making it a much more environmentally-friendly system,” Dr. Shetty said. “We expect this to pave the way towards more sustainable yet equally efficient photocatalytic systems for CO2 reduction.” Currently, Dr. Shetty’s team at KU is working on economically viable COF-based photoconducting materials for CO2 conversion.

Dr. Shetty is also a member of the Center for Catalysis and Separation (CeCaS), one of the research centers at KU.

Jade Sterling
Science Writer
4 February 2022

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The Undergraduate Research Competition (URC) is one of the largest competitions in the GCC that promotes scientific research among undergraduate students and supports the UAE government’s initiative of fostering innovation and empowering the youth to prepare them for the future. This is the eighth year of the competition and the research event has attracted creative minds not only from the GCC but in other countries as well such as Indonesia, Malaysia, Malta, and Morocco.

Around 315 original research papers were presented from 87 major universities in different disciplines, including engineering, natural and health sciences, business administration, education and law, and arts and social sciences.

The Chemical Engineering senior project of Khalifa University students Muna Al Jasmi, Anfal Abloushi, Shamma Thani, Reem Saeed Salem, and Ali Ahmed Algallaf, supervised by Prof. Lourdes Vega and Dr. Daniel Bahamon, won second place in the Chemical and Petroleum Engineering Category of the competition, with the project titled “Design of an Adsorption Air-Conditioning System Using Low Global Warming Potential (GWP) Refrigerants.”

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“This system is the first of its kind in the region and considered as one of the most promising technologies because of its advanced features as it does not depend on the electric energy generated from fossil fuels. It can work using electricity from renewable sources and a great alternative from an economical as well as environmental point of view,” Muna said. She explained that the system uses water as the refrigerant that provides powerful cooling while at the same time offers a sleek design that incorporates simple construction, easy control, quiet operation with no vibration, and low maintenance.

Cooling systems are an essential technology in our life, especially in arid and semi-arid regions, like the UAE.

“Current air-conditioning and refrigeration systems are energy-intensive, consuming around 17 percent of the global electricity production and more than 60 percent in the Emirates, representing a major impact on global warming and climate change. Moreover, the primary refrigerants used today have a high global warming potential (GWP), being thousands of times more potent greenhouse gases than carbon dioxide. Hence, active work is needed to replace them with low GWP refrigerants and to find more efficient cooling equipment. In their research project, our group of students proposed and designed an adsorption refrigeration system as an alternative to the compression system using water as the refrigerant, a silica-gel as the adsorbent, and a solar collector to provide the heat source to operate the system, a creative system with much lower impact into the environment than the ones currently used, representing a step forward on solving this very important environmental issue,” Dr. Vega said.��

“Obtaining second place in such a strong competition is a well-deserved recognition of their hard and innovative work and we are so proud of them!” she added.

The design the team came up with can be used here in the UAE and in other countries with similar weather conditions.��

“This project gave us an opportunity to apply the chemical engineering knowledge we gained during our academic journey to find and implement a solution to a major climate dilemma. We expect that in the near future, these novel technologies will change the whole scenario of sustainability, and will position the UAE to become a pioneer in the field of the new green economy globally,” Muna added.

Dr. Fawzi Banat, Professor and Chair of the Chemical Engineering Department, commented, “In the Shanghai Global Ranking of Academic Subjects 2021, which is dedicated to academic institutions for teaching and research, the Department of Chemical Engineering is ranked among the top 76-100. To achieve this ranking, the department achieved high scores on all of the analyzed indicators, which include articles indexed in Web of Science, the total number of citations, citations per article, articles published in the top 25% of scientific journals, and international interaction developed through collaborations with foreign institutions.”

“The department is dedicated to research and teaching excellence and currently offers doctoral, master’s, and bachelor’s degrees,” Dr. Banat added.��

The UAE actively supports a knowledge-based economy transformation, and events such as the URC encourages students to be more involved in accelerating the research needed to drive innovation in the country.

Ara Maj Cruz
Creative Writer
5 August 2021

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By Dr. Ludovic �ٳܳ�é��

Dr. Ludovic �ٳܳ�é�� , Assistant Professor of Chemical Engineering at Khalifa University, outlines the strategies and technologies that could be deployed to turn CO2 emissions into a resilient circular economy.

Read Arabic story .

The continuous emission of carbon dioxide into the atmosphere is the leading cause of climate change and subsequent extreme weather events.

In 2015, the international community adopted the Paris Climate Agreement, agreeing to limit the global average rise in temperature to less than 2° C, compared to pre-industrial levels, but with ambitions to limit the rise to less than 1.5° C. Along with a paradigm shift from fossil fuels to renewable energy sources, deployment of carbon capture and storage technologies was proposed as a core strategy to actively and significantly reduce greenhouse gas emissions. This is in addition to the clear economic benefit that could be derived from using CO2 as a feedstock material for chemical products in a resilient circular economy.

While research into CO2 capture technologies is gaining traction, research into integrated capture and conversion strategies – which involves capturing CO2 at its source and effectively transforming the CO2 into value-added chemicals within the same chemical process – has received significantly less attention.

With my colleagues from Deakin University in Australia, including Dr. James Maina, Prof. Jennifer Pringle and Prof. Joselito Razal, and Dr. Suzana Nunes from King Abdullah University of Science and Technology in Saudi Arabia, Dr. Fausto Gallucci from Eindhoven University of Technology in Netherlands, and Dr. Lourdes Vega, Director of Khalifa University’s Research and Innovation Center on CO2 and Hydrogen (RICH), we published a review paper in the journal to assess recent advances in the integrated capture and conversion of CO2 from industry gases and atmospheric air.

Carbon capture and storage technologies (CSS) have been demonstrated across a number of pilot operations globally and typically include capturing CO2 from emission sources such as power plants, followed by compression prior to transportation to long-term storage sites. Although CSS technologies are viable for the capture of CO2 from large sources at high concentration levels, such as fossil fuel power plants or cement factories, they are not practical for small and distributed sources, such as transportation and residential heating, which cumulatively account for around half of all CO2 emissions.

For these cases, technologies that can extract CO2 directly from the atmosphere are needed if the associated carbon emissions are to be mitigated. These are direct air capture technologies (DAC) and they have some distinct advantages over traditional carbon capture technologies, including not needing to be located close to emission sources, which makes them deployable to any location around the world. However, since there is a much lower concentration of CO2 in the atmosphere compared to that available in the by-product gas from industrial plants, DAC is much more costly and energy intensive.

Associated with carbon capture and storage is carbon capture and utilization (CCU) where the CO2 captured from various sources is put back to work as a raw material. While CCU is most often associated with Enhanced Oil Recovery, CO2 can also produce valuable chemicals and fuels, which may be marketed to generate revenue and offset the expenses associated with the capture process. With a suitable catalyst, CO2 can be converted into a wide variety of products, including acids, monomers and carbon nanomaterials.

The potential for developing profitable businesses from products generated from CO2 is evidenced by the large number of recent start-up companies. The annual methanol market, for example, is expected to reach US$91.5 billion by 2026 and since methanol can be made from hydrogen and CO2, this represents a significant opportunity.

However, to further minimize energy requirements and eliminate the risk of secondary CO2 emissions, new, sustainable and energy efficient materials and processes that capture and convert CO2 emissions from the air directly need to be developed.

In our paper, we recommend that conversion reactions be carried out using renewable energy and that any chemicals and catalyst materials be produced using sustainable methods. Otherwise, CO2 derived products won’t have a low carbon footprint compared to fossil-fuel derived products. To highlight this, the generation of methanol from a reaction between CO2 and hydrogen generated by reforming of natural gas was found to release three times more CO2 than the conventional industrial production technique. But when the same reaction was carried out with hydrogen generated from wind power, there was a 58 percent reduction in emissions.

There is great potential in the scale-up and commercialization of capture and conversion technologies, but there are also key technological challenges hindering the advancement of this field that research can help overcome. Research and development carried out in the RICH Center at Khalifa University is tackling some of these challenges from a different angle.��

Dr. Ludovic �ٳܳ�é�� is an Assistant Professor of Chemical Engineering at Khalifa University and a faculty member of the Research and Innovation Center on CO2 and Hydrogen (RICH).��

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