From a thermodynamic point of view, the possibility of intermolecular binding depends entirely on the binding free energy (∆G b ), which corresponds to the change in free energy during complexation of host and guest molecules and is closely related to the environmental temperature. At a given temperature, if ∆G b is clearly negative/positive, then the formation of the complex should be thermodynamically spontaneous/infeasible. We calculated the ∆G b of C 18 @OPP at different temperatures and further decomposed it as ∆G b = ∆H b -T∆S b , where ∆H b and ∆S b respectively represent the change of enthalpy and entropy upon binding, for illustrating the thermodynamic nature of formation of complex (Figure ). It can be seen from the ∆H b curve that the binding of C 18 to OPP is mainly driven by a significant reduction in enthalpy, and the extent of which is less temperature-dependent. The formation of host-guest complex C 18 @OPP reduces the freedom of motion of the system, so the entropy of the system is significantly decreased, leading to an obvious increase in the -T∆S b term. The overall result is that the ∆G b value of the C 18 @OPP increases with the rise of temperature, and it is expected that the supramolecular complex should spontaneously form below 404 K, because the calculated ∆G b of the system is negative in this temperature range. Since the introduction of a second C 18 molecule into OPP is almost unaffected by the composite center already formed in C 18 @OPP, the binding character for the second C 18 to OPP must be similar to those discussed above and will not be repeated here.