Sub-second Nanocomposite Synthesis in Continuous Flow Supercritical CO2 Reactor

Abstract

Metal-organic frameworks (MOFs) have attracted considerable scientific attention due to their diverse potential applications. However, to be viable for large-scale industrial use, MOFs must exhibit the intended functionality and properties and be produced and processed in an economically scalable manner that yields high-quality products with minimal environmental impact. In light of growing environmental concerns and commercial constraints, synthetic methods must prioritize eco-friendliness.This dissertation presents a method for synthesizing MOF composites using supercritical fluid as a reaction medium and a continuous flow process with short residence times. In the supercritical phase, fluids exhibit high sensitivity to minor changes in temperature or pressure, which can result in significant alterations in their thermophysical properties. This characteristic provides an exceptional opportunity to improve heat transfer in a mixing environment for synthesizing the nanocomposite. The use of this method enables a more efficient and environmentally friendly route to scale up the production of MOFs, incorporating principles of Green Chemistry. The initial focus of this dissertation is the refinement of a continuous flow supercritical reactor for synthesizing HKUST-1, a type of copper-based MOF. This research has led to the fastest-ever reported the synthesis of HKUST-1 in the scientific literature. Expanding upon the work with the continuous flow scCO2 reactor, the second part of this dissertation involved the synthesis of GO@HKUST-1 and CNT@HKUST-1 composite materials using the optimized continuous flow scCO2 reactor. The production rate achieved was multiple magnitudes greater than previous state-of-the-art methods. Moreover, a detailed mechanistic study comprising five experiments was conducted to investigate the impact of scCO2 injection temperature variation on the properties of GO@HKUST-1 and CNT@HKUST-1.