Adaptive Pores: Reversible Pore Engineering of Mesoporous Silica

Non-covalent and dynamic covalent methods were used to reversibly modify the pore size and philicity of mesoporous silica. In the non-covalent approach, the strong, charge-transfer interactions between pyranine and viologen moieties were usedfor reversible pore engineering.The fast binding of donors enabled quick and facile functionalization at room temperature. The viologen based charge transfer modules were employed in electrostatic gating of ion transport through the nanochannels (<10 nm)  in mesoporous silica. The polarity of ion transport was switched from anion selective to cation selective through ambipolar stage by controlling the extent of pyranine bound to the viologen. Further, the ion transport could be regulated with respect to pH by selecting a donor (coronenetetracarboxylate) with pH responsive functional groups. In the dynamic covalent approach, the reversible bonding between amine and aldehyde has been utilized to reverse the pore properties of silica. The modularity of the approach enables modification of nanopores with custom designed compositions, components and functions.