Synthesis-Structure-Property Relationships for Hyperbranched Aminosilica CO2 Adsorbents

Hyperbranched aminosilica (HAS) adsorbents are prepared via the ring‐opening polymerization of aziridine in the presence of mesoporous silica SBA‐15 support. The aminopolymers are covalently bound to the silica support and capture CO2 reversibly in a temperature swing process. Here, a range of HAS materials are prepared with different organic loadings. The effects of organic loading on the structural properties and CO2 adsorption properties of the resultant hybrid materials are examined. The residual porosity in the HAS adsorbents after organic loading, as well as the molecular weights and degrees of branching for the separated aminopolymers, are determined to draw a relationship between adsorbent structure and performance. Humid adsorption working capacities and apparent adsorption kinetics are determined from experiments in a packed‐bed flow system monitored by mass spectrometry. Dry adsorption isotherms are presented for one HAS adsorbent with a high amine loading at 35 and 75 °C. These combined results establish the relationships between adsorbent synthesis, structure, and CO2 adsorption properties of the family of HAS materials. The synthesis of hyperbranched aminosilica (HAS) solid CO2 adsorbents is modified to obtain materials with varied amine loadings. The composition and structure of the materials, as well as the aminopolymers grown off of the support, are characterized by an array of techniques and correlated to their measured adsorption performance (see figure).