According to Structural Materials and Global Climate, building construction and use accounts for an estimated 40 per cent of emissions, so the development of sustainable alternatives to existing materials could help mitigate climate change and reduce carbon dioxide emissions.
Addressing both issues simultaneously, materials scientist Muhammad Rahman and collaborators found a way to incorporate molecules of a carbon dioxide-trapping crystalline porous material into wood, according to a study published in Cell Reports Physical Science.
“Wood is a sustainable, renewable structural material that we already use extensively,” Rahman said in a statement. “Our engineered wood did exhibit greater strength than normal, untreated wood.”
To achieve this, the network of cellulose fibres that gives wood its strength is first cleared out through delignification.
“Wood is made up of three essential components: cellulose, hemicellulose and lignin,” said Rahman. “Lignin is what gives wood its colour, so when you take lignin out, the wood becomes colourless. Removing the lignin is a fairly simple process that involves a two-step chemical treatment using environmentally benign substances. After removing the lignin, we use bleach or hydrogen peroxide to remove the hemicellulose.”
The delignified wood is then soaked in a solution containing microparticles of a Calgary framework 20 (CALF-20) metal-organic framework (MOF). MOFs are a class of porous materials that can exhibit very high surface areas that have potential for applications including gas storage and separation, plus catalysis.
“The MOF particles easily fit into the cellulose channels and get attached to them through favourable surface interactions,” said Soumyabrata Roy, a Rice research scientist and lead author on the study.
According to Rice, MOFs are among several nascent carbon capture technologies developed to address anthropogenic climate change.
“Right now, there is no biodegradable, sustainable substrate for deploying carbon dioxide-sorbent materials,” Rahman said. “Our MOF-enhanced wood is an adaptable support platform for deploying sorbent in different carbon dioxide applications.”
“Many of the existing MOFs are not very stable in varying environmental conditions,” Roy said. “Some are very susceptible to moisture, and you don’t want that in a structural material.”
CALF-20, developed by University of Calgary Professor George Shimizu and collaborators, shows promise in terms of performance level and versatility under a variety of environmental conditions.
“The manufacturing of structural materials such as metals or cement represents a significant source of industrial carbon emissions,” Rahman said. “Our process is simpler and ‘greener’ in terms of both substances used and processing by-products.
“The next step would be to determine sequestration processes as well as a detailed economic analysis to understand the scalability and commercial viability of this material,” he added.
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