Periodic Reporting for period 1 - HANDLECO2 (High-performance adsorbents based on robust bijels stabilized by cellulose nanocrystals for direct air capture of CO2)
Période du rapport: 2023-06-15 au 2025-06-14
The average concentration of atmospheric CO2 has shown a remarkable increase, ranging from 172 to 300 ppm before the latest industrial age to ~420 ppm at present day. Past decades have witnessed great concerns about the catastrophic consequences resulting from ever-rising CO2 emissions, e.g. global warming, ocean acidification, and many other environmental and climate change issues. Direct air capture (DAC) has established itself as a promising technology to lower the atmospheric CO2 concentration permanently, thus contributing to climate change mitigation. Considering the billions of tons of CO2 that need to be captured, high-performance chemisorbents from the most abundant natural polymer, i.e. cellulose, are of great significance for the practical application of such negative emission technology. The main objective is to construct high-performance cellulosic DAC chemisorbents based on robust bijels, which are an emerging class of soft solid materials with interconnected hierarchical pore networks and semipermeable interfacial layers. Cellulose nanocrystals (CNCs) with surface-immobilized 10-undecenoyl groups will be synthesized and then modified by clickable poly(ionic liquid)s (PILs) via simple thiol-ene click chemistry. The surface chemistry of PILs-modified CNCs will further be tuned by a simple counterion exchange method. Next, the applicant will fabricate bijels of high stability by new methods to crosslink the CNCs with designed surface chemistry at the fluid-fluid interface. The robust bijels stabilized by CNCs will then be processed into aerobijels via simple freeze-drying. The numerous accessible amine groups on CNCs, in combination with the bicontinuous porous structure and semipermeable interfacial layers of the final aerobijels, will allow for high CO2 adsorption capacity and fast CO2 adsorption kinetics.
Microcrystalline cellulose derived from cotton was used to fabricate cellulose aerogel as porous support via a NaOH/urea-based dissolution and regeneration process, followed by surface modification with a series of amino silane coupling agents to produce aminated cellulose aerogel as CO2 adsorbent. The as-synthesized optimal adsorbent exhibited a high CO2 sorption capacity of up to 1.5 mmol/g and 1.3 mmol/g at 0 °C and 25 °C at 1 bar, respectively. Notably, in-depth analysis showed that the adsorbent achieved an impressive capacity of CO2 uptake of 0.29 mmol/g at 25 °C at an exceptionally low CO2 pressure of 0.4 mbar, i.e. under ambient CO2 pressure. It implies its potential use as adsorbent both for the traditional point-source capture and the direct air capture as an emerging negative emission technology.
Our results indicate that porous aerogels derived from cellulose hold significant potential for capturing CO2 under ambient conditions. However, challenges remain with CO2 adsorption capacity and kinetics, which must be addressed to advance practical applications. CNCs-based aerobijels, offering abundant adsorption sites and optimized pore structures, present a promising material option and warrant further investigation, as our current findings suggest.