Supporting\nPorous Metal–Organic Frameworks\non Carboxylated-Wood Sponges for Direct Air Capture and Highly Selective\nCO<sub>2</sub>/CH<sub>4</sub> Separation

To effectively mitigate the global\nwarming problem caused by excessive\nCO<sub>2</sub> emissions, the implementation of direct air capture\n(DAC) technology has emerged as one of the most promising strategies\nfor capturing CO<sub>2</sub> from the atmosphere. The key to DAC technology\nhinges on the development of high-performance solid sorbent materials\nthat demonstrate high CO<sub>2</sub> adsorption capacity and gas separation\nselectivity, particularly under low CO<sub>2</sub> partial pressure\nconditions. Herein, we have successfully developed a class of MOF@carboxylated\nwood sponge (MOF@CWS) hybrid sorbents, capable of efficient CO<sub>2</sub> capture from low-concentration (less than 10,000 ppm) CO<sub>2</sub> sources, achieved by embedding the porous MOF into carboxylated\nwood sponges (CWS) substrate via an in situ growth route. Within the\nMOF@CWS series, the CO<sub>2</sub> uptake capacity of Mg-MOF-74@CWS\nis 3.61 and 2.65 mmol/g at 1 bar, 273 and 298 K, respectively, significantly\nhigher than those of CWS and HKUST-1@CWS. Moreover, this material\nexhibited outstanding DAC performance, with the CO<sub>2</sub> sorption\ncapacity at 273 K up to 0.56 mmol/g from ambient air (ca. 400 ppm\nof CO<sub>2</sub>), surpassing most other solid sorbents. The obtained\nMg-MOF-74@CWS also demonstrated exceptional CO<sub>2</sub>/CH<sub>4</sub> separation performance, primarily due to the unique pore\nstructure and augmented interaction between the CO<sub>2</sub> molecules\nand the hybrid sorbents. The results of this study indicate that Mg-MOF-74@CWS\nhas potential as an efficient solid sorbent for the DAC of CO<sub>2</sub>.