A novel synthesis of a new thorium (IV) metal organic framework nanostructure with well controllable procedure through ultrasound assisted reverse micelle method

Reverse micelle (RM) and ultrasound assisted reverse micelle (UARM) were applied to the synthesis of novel thorium nanostructures as metal organic frameworks (MOFs). Characterization with different techniques showed that the Th-MOF sample synthesized by UARM method had higher thermal stability (354 °C), smaller mean particle size (27 nm), and larger surface area (2.02 × 103 m2/g). Besides, in this novel approach, the nucleation of crystals was found to carry out in a shorter time. The synthesis parameters of UARM method were designed by 2k−1 factorial and the process control was systematically studied using analysis of variance (ANOVA) and response surface methodology (RSM). ANOVA showed that various factors, including surfactant content, ultrasound duration, temperature, ultrasound power, and interaction between these factors, considerably affected different properties of the Th-MOF samples. According to the 2k−1 factorial design, the determination coefficient (R2) of the model is 0.999, with no significant lack of fit. The Fvalue of 5432, implied that the model was highly significant and adequate to represent the relationship between the responses and the independent variables, also the large R-adjusted value indicates a good relationship between the experimental data and the fitted model. RSM predicted that it would be possible to produce Th-MOF samples with the thermal stability of 407 °C, mean particle size of 13 nm, and surface area of 2.20 × 103 m2/g. The mechanism controlling the Th-MOF properties was considerably different from the conventional mechanisms. Moreover, the MOF sample synthesized using UARM exhibited higher capacity for nitrogen adsorption as a result of larger pore sizes. It is believed that the UARM method and systematic studies developed in the present work can be considered as a new strategy for their application in other nanoscale MOF samples.