Direct Access to Primary Amines and Particle Morphology Control in Nanoporous CO2 Sorbents

Chemical tuning of nanoporous, solid sorbents for ideal CO2 binding requires unhindered amine functional groups on the pore walls. Although common for soluble organics, post-synthetic reduction of nitriles in porous networks often fails due to insufficient and irreversible metal hydride penetration. In this study, a nanoporous network with pendant nitrile groups, microsphere morphology was synthesized in large scale. The hollow microspheres were easily decorated with primary amines through in situ reduction by widely available boranes. The CO2 capture capacity of the modified sorbent was increased to up to four times that of the starting nanoporous network with a high heat of adsorption (98 kJ mol−1). The surface area can be easily tuned between 1 and 354 m2 g−1. The average particle size (ca. 50 μm) is also quite suitable for CO2 capture applications, such as those with fluidized beds requiring spheres of micron sizes.