Designed Synthesis of Mesoporous Solid-Supported Lewis Acid–Base Pairs and Their CO2 Adsorption Behaviors

Abstract

Conventional amines and phosphines, such as diethylenetriamine, diphenylpropylphosphine, triethylamine, and tetramethylpiperidine, were grafted or impregnated on the surface of metalated SBA-15 materials, such as Ti-, Al-, and Zr-SBA-15, to generate air-stable solid-supported Lewis acid-base pairs. The Lewis acidity of the metalated materials before and after the introduction of Lewis bases was verified by means of pyridine adsorption-Fourier transform infrared spectroscopy. Detailed characterization of the materials was achieved by solid-state 13C and 31P MAS NMR spectroscopy, low-temperature N2 physisorption, X-ray photoelectron spectroscopy, and energy-dispersive X-ray mapping analyses. Study of their potential interactions with CO2 was performed using CO2 adsorption isotherm experiments, which provided new insights into their applicability as solid CO2 adsorbents. A correlation between solid-supported Lewis acid-base pair strength and the resulting affinity to CO2 is discussed based on the calculation of isosteric enthalpy of adsorption.