Continuous and ultrafast MOF synthesis using droplet microfluidic nanoarchitectonics

Abstract

Metal–organic frameworks (MOFs) constitute a class of porous materials with widespread applications owing to their remarkable and tunable properties. Although MOFs are currently the leading examples of porous materials, they are yet to demonstrate promising progress in industrial applications due to limitations in the current production processes, such as the requirement of excess solvent, intensive labor requirements, and long processing times. Herein, we propose a continuous droplet microfluidic system to accelerate the generation of MOFs and to achieve scalable continuous production. The results demonstrate the formation of uniform MOFs within 3 min using a microfluidic system, which is much faster than the conventional hydrothermal synthesis that requires 300 min. By precisely controlling the flow rates of the two phases, we enhanced productivity and generated minimum droplets to create a restricted microreactor. We also observed that the crystallinity of ZIF-8 and MIL-100 improved significantly with increasing synthesis temperature. We have also provided a de novo method for the one-pot synthesis of gold-encapsulated ZIF-8, overcoming the disadvantages of impregnation, precipitation, or ion exchange associated with metal immobilization on MOFs. Overall, the novel microfluidic system proposed herein achieves rapid and scalable continuous production of MOFs under mild conditions.