Organic phthalocyanine derivatives for NIR reflective coatings

Urban heat island effects are mainly caused by near infrared region (NIR) thermal radiation (700–2500 nm) produced by sunlight. To reduce accumulation of heat, cooling paintings containing NIR reflective pigments is one possible solution. In this research, 4-tert-butyl phthalocyanines were synthesized through environmentally friendly solvent-free methods. The NIR reflective behaviors could be readily tuned through modification of phthalocyanines structures, and it was found out that the distribution state of the electron in d orbit plays a key role in determining the intensity of NIR reflectance. 4-tert-butyl Cu(II) phthalocyanine showed the highest total solar reflectance (73 %) among all synthesized phthalocyanines, and It exhibited good heat resistance, weathering stability. Eventually, the film prepared by mixing polydimethylsiloxane and 4-tert-butyl Cu(II) phthalocyanine (PDMS-Pc) showed a temperature difference of 7.5 °C compared to pure polydimethylsiloxane film in the model house study, demonstrating potential applications as cooling coatings. This cooling coating material can reduce the energy consumption caused by cooling equipment such as air conditioners which will achieve energy conservation in the future.