Carbon dioxide is the main greenhouse gas warming Earth and is emitted in large quantities in the flue gases from industrial and power plants. A new method for removing CO2 from these flue gases involves piping the emissions through a porous material based on the chemical melamine. DETA, a chemical bound inside the porous melamine, grabs CO2 and removes it from the gas, with nitrogen vented to the atmosphere. Using an inexpensive polymer called melamine—the main component of Formica—chemists have created a cheap, easy and energy-efficient way to capture carbon dioxide from smokestacks, a key goal for many countries as they seek to reduce greenhouse gas emissions.
In a new study published in journal Science Advances, researchers lead by Jeffrey Reimer, Professor of the Graduate School in the Department of Chemical and Biomolecular Engineering at the University of California, Berkeley developed a new process for synthesizing the melamine material could potentially be scaled down to capture emissions from vehicle exhaust or other movable sources of carbon dioxide. Carbon dioxide from fossil fuel burning makes up about 75% of all greenhouse gases produced in the U.S. The new material is simple to make.
The authors focused on cheaper material design for capture and storage and elucidating the interaction mechanism between CO2 and the material. This work creates a general industrialization method towards sustainable CO2 capture using porous networks. The authors hope to design a future attachment for capturing car exhaust gas, or maybe an attachment to a building or even a coating on the surface of furniture. The melamine porous network with DETA and cyanuric acid modification captures CO2 at about 40 degrees Celsius, slightly above room temperature, and releases it at 80 degrees Celsius, below the boiling point of water. The energy savings come from not having to heat the substance to high temperatures.
The research team focused on the common polymer melamine, which is used not only in Formica but also inexpensive dinnerware and utensils, industrial coatings and other plastics. Treating melamine powder with formaldehyde which the researchers did in kilogram quantities creates nanoscale pores in the melamine that the researchers thought would absorb CO2. The researchers confirmed that formaldehyde-treated melamine adsorbed CO2 somewhat, but adsorption could be much improved by adding another amine-containing chemical, DETA (diethylenetriamine), to bind CO2. She and her colleagues subsequently found that adding cyanuric acid during the polymerization reaction increased the pore size dramatically and radically improved CO2 capture efficiency: Nearly all the carbon dioxide in a simulated flue gas mixture was absorbed within about 3 minutes.
They conducted solid-state nuclear magnetic resonance (NMR) studies to understand how cyanuric acid and DETA interacted to make carbon capture so efficient. The studies showed that cyanuric acid forms strong hydrogen bonds with the melamine network that helps stabilize DETA, preventing it from leaching out of the melamine pores during repeated cycles of carbon capture and regeneration. They were able to show with these elegant techniques is exactly how these groups intermingle, exactly how CO2 reacts with them, and that in the presence of this pore-opening cyanuric acid, she’s able to cycle CO2 on and off many times with capacity that’s really quite good. The rate at which CO2 adsorbs is actually quite rapid, relative to some other materials. So, all the practical aspects at the laboratory scale of this material for CO2 capture have been met, and it’s just incredibly cheap and easy to make. Professor Reimer and colleagues are continuing to tweak the pore size and amine groups to improve the carbon capture efficiency of melamine porous networks, while maintaining the energy efficiency. This involves using a technique called dynamic combinatorial chemistry to vary the proportions of ingredients to achieve effective, scalable, recyclable and high-capacity CO2 capture.
Mao H, Tang J, Day GS, Peng Y, Wang H, Xiao X, Yang Y, Jiang Y, Chen S, Halat DM, Lund A, Lv X, Zhang W, Yang C, Lin Z, Zhou HC, Pines A, Cui Y, Reimer JA. A scalable solid-state nanoporous network with atomic-level interaction design for carbon dioxide capture. Sci Adv. 2022;8(31):eabo6849. doi: 10.1126/sciadv.abo6849.