Amine-grafted on boron modified SBA-15 for direct air capture of CO2

Amine loading was considered to be the main factor affecting the CO2 capture performance of amine-grafted mesoporous materials. In this study, SBA-15 with varied boron loadings was investigated to understand the effect of amine loading on the CO2 adsorption ability. It was found that the dynamic CO2 capacity with respect to boron loading showed a volcano curve. Proper boron additives with acid treatment could improve the amount of silanol in SBA-15. Temperature programmed desorption results indicated that the dynamic CO2 capacity was in linear relationship with the amine loading, which was decided by silanol via its reaction with graft amines. Moreover, amine grafted SBA-15 with boron additive showed good cyclic stability and vapor resistance. In situ-DRIFTS showed that surface silanol groups participate in the CO2 capture process by forming carbamic acid (hydrogen-bonded) and silylpropylcarbamate. These results provide a quantitation understanding between dynamic CO2 capacity, amine loading and hydroxyl groups, which would provide a guideline for the development of high dynamic CO2 capacity in the direct air capture.