Fig. 4. (a) UV-vis spectrum change for the isomerization of COF-HNU9-O (1) to COF-HNU9-C (2) upon irradiation with a 515 nm light and for the recovery of the UV-vis spectra of COF-HNU9-O upon mild heating at 40 °C in the dark under 32% RH (3); (b–d) contact angle of a water droplet on a COF-HNU9-coated glass surface before and after visible light-irradiation and reversed by heating (corresponding to (1)–(3) in (a)).
