transition from BTC3 to Cu2+ was enhanced for the first two addition procedures. This enhanced absorption of the LMCT process (Fig. S6†) could be attributed to the increased thickness of the MOF shells. With further addition of the HKUST-1 precursor, the pitches of the resulting helical MOFs got longer and finally disappeared (Fig. 2d and S5†), resulting in the CD signals assigned to the LMCT transition being weakened and/or having disappeared. Fig. S6 and S7† show the evolution of the UV-vis spectra of the reaction system with different MOF precursor concentrations and MOF crystal deposition times, respectively. It was found that in both cases the absorption band of the as-prepared helical MOF nanowires only changed in intensity, while the location remained unchanged. This result indicates that the coordination of the carboxylate groups on the template surface with metal ions hardly exerts a marked influ-
ence on the structure of the deposited MOF material. The MOF deposited on the template surface has the same structure as that of the conventional MOF. Thus, variations in the LMCT and d–d transitions within the helical conformation were not detected in our case.