A new pure organic co-crystal compound 1, [C4H4O4][C8H19N] ([C4H4O4] = maleic acid, [C8H19N] = diisobutylamine/DIBA) was discovered to undergo an above room temperature reversible phase transition at around 353/343 K. The variable-temperature single-crystal X-ray structural measurements reveal that space group of the structural phase transition is from space group Cmm2 to space group Imm2. The phase transition of compound 1 is mainly ascribed to the twisted movement of diisobutylamine molecules. Meanwhile, nonlinear optical (NLO) properties were also observed in compound 1.

The paper focuses on a new type of solar collector used double plastic-steel windows and covered of double common glasses. To ensure air passage closed and insulation, the collector is prefabricated made in whole. The inside and backplane of collector are covered of heated enamel in dark green with copper oxide, magnesium oxide and iron oxide; The penetrated metal mesh is placed in air passage between absorber and glasses to enhance heat transfer. The size and position of gas inlet and outlet of collector could be specified by means of simulation and analysis. Heat loss coefficients and thermal efficiency are tested. The results show that thermal efficiency of collector is superior and performance of heat preservation is good. The application of collector in solar buildings can replace the Trombe wall and be used as a type of outdoor, easy to regulate their construction process and ensure the effect of solar collector.