Solventless synthesis of ZIF-L and ZIF-8 with hydraulic press and high temperature

Abstract

In recent years, alternative methods to conventional synthesis of MOFs (metal-organic frameworks) have emerged due to the problematic use of solvents for both the environment and human health. Here we present the synthesis of ZIFs (zeolitic imidazolate frameworks) at high pressure by means of a hydraulic press provided with a heating mechanism. By the optimization of parameters such as temperature, time and the addition of promotor NH4NO3, a considerable increase in the reaction yield was achieved in products, neither washed nor activated, obtained since the first minute of reaction. Depending on the operation conditions, ZIF-L appeared as competing phase with ZIF-8. Upon transformation of ZIF-L into ZIF-8 in presence of ethanol, a reaction yield of 58.2% was achieved to highly crystalline ZIF-8 with a BET specific surface area of 947 m2/g. This green, fast, versatile and improved method suggests a possible way to future synthesis of other MOFs and the possibility of their industrial implementation.