Strong Foam-like Composites from Highly Mesoporous Wood and Metal-Organic Frameworks for Efficient CO₂ Capture

Mechanical stability and multicycle durability are essential for emerging solid sorbents to maintain an efficient CO₂ adsorption capacity and reduce cost. In this work, a strong foam-like composite is developed as a CO₂ sorbent by the in situ growth of thermally stable and microporous metal-organic frameworks (MOFs) in a mesoporous cellulose template derived from balsa wood, which is delignified by using sodium chlorite and further functionalized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation. The surface carboxyl groups in the TEMPO-oxidized wood template (TO-wood) facilitate the coordination of the cellulose network with multivalent metal ions and thus enable the nucleation and in situ growth of MOFs including copper benzene-1,3,5-tricarboxylate [Cu₃(BTC)₂], zinc 2-methylimidazolate, and aluminum benzene-1,3,5-tricarboxylate. The TO-wood/Cu₃(BTC)₂ composite shows a high specific surface area of 471 m² g^-1 and a high CO₂ adsorption capacity of 1.46 mmol g^-1 at 25 °C and atmospheric pressure. It also demonstrates high durability during the temperature swing cyclic CO₂ adsorption/desorption test. In addition, the TO-wood/Cu₃(BTC)₂ composite is lightweight but exceptionally strong with a specific elastic modulus of 3034 kN m kg^-1 and a specific yield strength of 68 kN m kg^-1 under the compression test. The strong and durable TO-wood/MOF composites can potentially be used as a solid sorbent for CO₂ capture, and their application can possibly be extended to environmental remediation, gas separation and purification, insulation, and catalysis.