Polyoxometalate-modified reduced graphene oxide foam as a monolith reactor for efficient flow catalysis of epoxide ring-opening reactions

Continuous flow catalysis has been attracting significant interest due to its remarkable advantages over traditional batch reactions. In this work, a facile and broad-spectrum hydrothermal approach has been developed to construct polyoxometalate-modified reduced graphene oxide (POM@rGO) foam, which worked as a monolith reactor for efficient continuous flow catalysis of epoxide ring-opening reactions. The porous structures of rGO foam allow the high dispersion of the POM catalyst onto the substrate through electrostatic interactions. Specifically, a phosphotungstic acid (H3PW12O40, denoted as PW12)-modified rGO (PW12@rGO) monolith reactor exhibits remarkable catalytic activity and durability towards epoxide ring-opening reactions with alcohols, achieving 99% conversion and 92% selectivity for the methanolysis product in 10 min under ambient conditions without stirring. Notably, while coupling with a micro-injection pump, such PW12@rGO foam can work as an efficient continuous flow reactor towards methanolysis of styrene oxide for 38 h with 99% conversion and over 90% selectivity, reaching a turnover number (TON) as high as 28 044.