Development of Multi-functional Catalysts for Capture and Catalytic Transformation of Carbon Dioxide Using Nanoporous Materials

Abstract

Carbon dioxide (CO₂) capture and storage (CCS) technologies and catalytic CO₂ transformation may become extremely important for mitigating global warming, but still present major challenges. Poly(ethyleneimine) (PEI) contains a high density of amine moieties in its polymer chain, so is considered one of the promising adsorbents for CCS technology. This review describes the design, preparation, and applications of multi-functional adsorbents and catalysts using PEI as CO₂ adsorbent and nanoporous materials as supports for efficient capture and catalytic transformation of CO₂. A series of PEI-mesoporous silica composites were prepared for CO₂ capture applications from simulated CO₂ gas streams with concentrations of 10 % and 400 ppm. Tuning of the surface acid/base properties of the mesoporous silicas via incorporation of heteroatoms (such as Zr and Ti) strengthened the interaction between PEI and the silica, resulting in significantly increased CO₂ adsorption capacities, improved CO₂ adsorption/desorption kinetics, and enhanced regeneration characteristics. Furthermore, hybrid catalysts consisting of metal complex/nanoparticles and PEI confined in chemically-stable nanoporous materials (such as titanate nanotubes and hollow mesoporous organosilica spheres) were fabricated for use as heterogeneous catalysts for hydrogenation of CO₂ to formic acid (HCOOH), which is a key reaction for sustainable hydrogen energy cycles. The CO₂ capture characteristics of PEI and the stabilizing effect of the support materials achieved high catalytic activity and reusability under moderate reaction conditions.