(a) Concentration dependence of diffusion coefficient D (CD3CN/CD2Cl2 = 1/1, v/v, 295 K, 400 MHz) of 6a; (b) Size distributions of 6a at different concentrations of B21C7 units in the mixture of CH3CN/CH2Cl2 (1/1, v/v); (c) G’ and G” versus ω for the gel with the concentration of B21C7 unit of 240 mM in CH3CN/CH2Cl2 (1/1, v/v); (d) SEM image of 6a with the concentration of B21C7 unit of 10 mM in CH3CN/CH2Cl2 (1/1, v/v). The scale bar is 1 μm.