Runaway Carbon Dioxide Conversion Leads to Enhanced Uptake in a Nanohybrid Form of Porous Magnesium Borohydride.

Abstract

Leveraging molecular-level controls to enhance CO₂ capture in solid-state materials has received tremendous attention in recent years. Here, a new class of hybrid nanomaterials constructed from intrinsically porous γ-Mg(BH₄ )₂ nanocrystals and reduced graphene oxide (MBHg) is described. These nanomaterials exhibit kinetically controlled, irreversible CO₂ uptake profiles with high uptake capacities (>19.9 mmol g^-1 ) at low partial pressures and temperatures between 40 and 100 °C. Systematic experiments and first-principles calculations reveal the mechanism of reaction between CO₂ and MBHg and unveil the role of chemically activated, metastable (BH₃ -HCOO)^- centers that display more thermodynamically favorable reaction and potentially faster reaction kinetics than the parent BH₄ ^- centers. Overall, it is demonstrated that size reduction to the nanoscale regime and the generation of reactive, metastable intermediates improve the CO₂ uptake properties in metal borohydride nanomaterials.