晶化后冷却方式诱导形成不同结构的微孔材料

An interesting result with the products of crystallization being dominated by the cooling rate has been raised in the crystallization of ethylenediamine (EDA)-directed cobalt phosphates and 1,2-diaminopropane (PDA) -directed zinc phosphates. To explore the reason and mechanism behind this phenomenon,these two systems were crystallized under different temperatures from 1 to 6 d followed by fast cooling (in 10 min) or slow cooling (in 3 h) route, respectively. The results showed that, within a certain range ofcrystallization time, slow cooling rate would result in a framework transformation. Further investigation indicates that this transformation is lower-temperature-preferable in EDA-CoPO4 system, and the slow cooling process give the system a period of time to carry out the transformation under lower temperature. However, in PDA-ZnPO4 system, a higher-temperature-preferable transformation has been found, and further study on SAPO-CHA presents a similar result, which is in consistent with general transformation conditions of most crystals, which protrudes the uniqueness of EDA-directed crystallization of cobalt phosphates systems.