With increasing global climate change, integrated concepts for innovating sustainable structures that can address CO2 mitigation multi-axially are critical. The construction and use of buildings are estimated to be responsible for 40% of carbon dioxide emissions, making structural elements such as steel or cement costly financially and environmentally.

Creating environmentally friendly alternatives to current materials can help slow global warming and reduce carbon dioxide emissions. Rice University scientists have developed a method to strengthen wood for use in the building while also designing it to retain carbon dioxide through a technique that can be scaled up and uses less energy.

Scientists have found a way to incorporate molecules of a carbon dioxide-trapping crystalline porous material into wood.

Materials scientist Muhammad Rahman said: “Wood is a sustainable, renewable construction material that we already use a lot. Our processed wood showed greater strength than normal, untreated wood.

“To achieve this feat, the network of cellulosic fibers that gives wood its strength is first cleaned up through a process known as delignification.”

“Wood consists of three essential components: cellulose, hemicellulose and lignin. Lignin gives wood its color, so if you take out lignin, the wood becomes colorless. Removing the lignin is a simple process consisting of a two-step chemical treatment with environmentally friendly substances. After removing the lignin, we use bleach or hydrogen peroxide to remove the hemicellulose.”

The lignified wood is then dipped in a solution containing small pieces of Calgary Framework 20 (MOF), a metal-organic framework (CALF-20). MOFs are high surface area absorbent materials used for their ability to adsorb carbon dioxide molecules in their pores.

Natural wood
Natural wood (left) versus refined wood. Removing lignin from wood makes it colorless. (Photo by Gustavo Raskosky/Rice University)

Soumyabrata Roy, a Rice researcher and lead author of the study, said: “The MOF particles easily fit into the cellulose channels and become attached to them through favorable surface interaction.”

Rahman said, “MOFs are among several burgeoning carbon capture technologies developed to address anthropogenic climate change. Currently, no biodegradable, sustainable substrate for using carbon dioxide sorbent materials exists. Our MOF-enhanced Wood is an adaptable support platform for deploying sorbent in various carbon dioxide applications.”

Roy said, “Many existing MOFs are unstable in changing environmental conditions. Some are sensitive to moisture and you don’t want that in building materials.”

“However, CALF-20 stands out both in terms of performance level and versatility under different environmental conditions.”

Rahman said, “Manufacturing structural materials such as metals or cement represents a major source of industrial carbon emissions. Our process is simpler and ‘greener’ in terms of used substances and processing of by-products.”

“The next step would be to determine capture processes as well as a detailed economic analysis to understand the scalability and commercial viability of this material.”

Magazine reference:

  1. Soumyabrata Roy, Firuz Alam Philip, et al. Functional wood for carbon dioxide capture | Cell Reports Natural Sciences | DOI: 10.1016/j.xcrp.2023.101269