Coffee Ground-Derived Carbon Molecular Sieves: Controllable Microdomain Structure Evolution for Sub-Angstrom Molecular Sieving of C4 Olefin Mixture

The conversion of low-cost biomass into advanced carbon molecular sieves (CMS) with molecule-recogniting precision is crucial for gas separations but remains challenging: biomass-derived carbon precursors are inherently amorphous, making it extremely difficult to control their pore size distributions at subangstrom scale. Addressing this gap, this study focuses on investigating controllable evolution of microdomain structure and surface chemistry in amorphous carbon precursor derived from coffee grounds and fabricating coffee ground-derived carbon molecular sieves (CFGCMS) from spent coffee grounds via controllable pyrolysis for separation of butadiene (C4H6), 1-butene (n-C4H8), and isobutene (i-C4H8). The resulting material, CFGCMS-800, exhibits selective adsorption of C4H6 while almost completely excluding both n-C4H8 and i-C4H8. Its IAST-predicted selectivities for C4H6/n-C4H8 and C4H6/i-C4H8 exceed 10,000. Breakthrough experiments further confirm the superior dynamic separation capability of CFGCMS-800 for the C4H6/n-C4H8/i-C4H8 ternary mixture. Additionally, the structure-performance relationship of these amorphous CFGCMS materials is clarified. This study demonstrates that biomass can be transformed into advanced CMS with subangstrom molecular recognition precision, comparable to crystalline MOF materials, thereby providing valuable guidance for the development of novel carbon molecular sieves from diverse biomass-derived carbon sources for gas separation applications.