Highly porous aerogels based on imine chemistry: syntheses and sorption properties

Abstract

A series of novel aerogels have been obtained based on imine chemistry. The aerogels were prepared by polycondensation of various bridging aldehydes and amines via a sol–gel process. The imine aerogels of tetrakis-(4-aminophenyl)methane (A1) consist of three-dimensional networks of interconnected nanometer-sized particles with hierarchically porous structures. The porosity of the areogels is tuneable by the choice of precursors, precursor concentration and reaction solvent. The aerogels exhibit BET surface areas up to 1021 m² g⁻¹ (A1-biformyl aerogel A1B1-0.030), as measured by N₂ adsorption at 77 K. The A1B1-0.030 aerogel possesses a CO₂ uptake of 1.5 mmol g⁻¹ at 298 K and 1.0 bar with an isosteric heat of 38.1 kJ mol⁻¹ and displays high CO₂/N₂ selectivity up to 70.9, which is derived from the ideal adsorbed solution theory. The A1B1-0.030 aerogel also shows a good capacity to uptake aromatic toluene molecules from an aqueous solution. Moreover, the hierarchically porous structure endows the A1B1-0.030 aerogel with good performance in enrichment of large molecules (polycyclic aromatic hydrocarbons PAHs and organochlorine pesticides OCPs) as the coating adsorbent in solid-phase microextraction (SPME) fibres.