In situ amino–lignin production via biomass fractionation for high-efficacy CO2 capture

Abstract

Amine-functionalized solid adsorbents (NFSAs) from green and renewable biomasses have been proven to be a significant breakthrough for utilizing renewable resources in the carbon capture and storage field. Lignin, a major biomass component, is an auspicious biomass-based adsorbent material owing to its rich chemical structure, abundant functional groups, and high stability. Inevitably, the carbon–carbon condensation during technical lignin isolation leads to heterogeneity, which restricts the lignin amination modification in NFSAs. Herein, we present a technology breakthrough in the direct production of aminated lignins with high N-density via the reactive fractionation of biomasses using an aniline–formic acid solvent system. This innovative strategy enabled in situ amination of lignins in high weight percent yields during the acid delignification of different biomasses and holistically produced high-purity cellulose (glucose yield above 95%). Here, aniline acted as a nucleophile to capture Cα carbocations in the lignin structure and selectively directed the condensation towards dominant α-amination, effectively inhibiting the uncontrolled lignin condensation to retain the chemical reactivity of lignin macromolecules. The nanomaterials further derived from these aminated lignin macromolecules offered promising perspectives as bio-based adsorbents for efficient CO₂ capture. Nanoparticles of amino–lignin in the size range of 339 ± 72 nm derived from the bamboo biomass demonstrated an exceptional adsorption capacity of 324 mg CO₂ per gram of adsorbent in a wet capture method. Comparison with existing industrial processes has demonstrated that our approach is green and sustainable, with potential commercial value for subsequent industrial applications and large-scale utilization. This proof-of-concept method highlights a significant advancement in carbon capture technologies, utilizing sustainable and biodegradable nanomaterials to address the pressing environmental challenges.