Aminosilane-functionalized Ti-based metal–organic framework for efficient and selective CO2 adsorption

Carbon dioxide capture and storage (CCS) is considered as a promising strategy for reducing CO 2 emissions. However, the further development of CO 2 adsorption materials with high selectivity and high adsorption capacity is the top priority of this technology . In this study, we used the μ-OH sites of the MIL-125 metal–organic framework (MOF) to modify it with aminosilane to synthesize a new MOF adsorbent (SAP-MIL-125) with improved CO 2 adsorption capacity at room temperature. Although there are no open metal sites on the MIL-125 surface, it is possible to load aminosilanes onto it. Under the same adsorption conditions, the CO 2 adsorption by SAP-MIL-125 was significantly improved compared to that of the original MIL-125. Adsorption isotherm and kinetics models were used to clarify that the adsorption mechanism of CO 2 on SAP-MIL-125 was non-homogeneous layer chemisorption . SAP-MIL-125 has excellent selectivity toward CO 2 (compared to N 2 ) and good stability over five adsorption–desorption cycles. The adsorption of CO 2 by SAP-MIL-125 is a spontaneous exothermic process. An in-depth investigation of the adsorption mechanism suggests that the acid–base interactions of carbamates is the mechanism of CO 2 adsorption. Density functional theory and frontier molecular orbital calculations showed that the main adsorption sites for the modified adsorbent were nitrogen-containing groups on the surface of aminosilanes, with the primary amines having the highest affinity for CO 2 . In conclusion, a novel material modification method for MOFs is provided, which was used to fabricate a CO 2 adsorbent with great potential for development.