Preparation and Gas Adsorption Characteristics of Zeolite MFI Crystals with Organic-Functionalized Interiors

We show that the selective gas adsorption properties of pure-silica MFI zeolite crystals are significantly altered by modifying their internal pore structure with molecules such as aliphatic alcohols, aromatic alcohols, amino-alcohols, and amines. NMR and TGA/DSC characterization indicates that the functional groups are chemisorbed to the internal pores, and the organic molecule loading is strongly dependent on the concentration of internal silanol sites. Adsorption isotherms of CO2, CH4, and N-2 are measured for the functionalized samples up to 400 kPa. In the low pressure region (1-10 kPa), the organic-modified materials show gas adsorption behavior significantly different from that of the bare zeolite MFI, ranging from an enhancement in CO2/CH4 sorption selectivity in the amine-functionalized materials to an enhancement in CH4 adsorption in the aromatic-functionalized material. The CO2/N-2 sorption selectivity decreases for all the modified materials compared to bare zeolite MFI. This investigation of organic-modified MFI zeolites points toward the tuning of adsorption and molecular sieving behavior of zeolites through internal modification of the pores.