Ag nanoparticles immobilized over highly porous crystalline organosilica for epoxidation of styrene using CO2 as oxidant

We report a new crystalline porous organosilica material, which stabilized tiny AgNPs to obtain a robust nanocatalyst Ag@TSOS-1 that efficiently catalyses the complete conversion of styrene into predominantly styrene oxide using CO 2 as an oxidant in a high pressure autoclave reactor. • A new crystalline porous organosilica material has been synthesized using a tailor made bridging organoslilane precursor. • Ag nanoparticles were supported over porous organosilica material to design a novel nanocatalyst Ag@TSOS-1. • Ag@TSOS-1 catalyses epoxidation of styrene to styrene oxide using CO 2 as soft oxidant. • At 20 bar CO 2 pressure and 60 °C temperature only styrene oxide and polystyrene formed from styrene. Selective epoxidation of olefins is a very important reaction as epoxides are widely been used as platform chemical in polymer and pharmaceutical industries. Unlike conventional oxidants like molecular O 2 or peroxides, the use of CO 2 as a soft oxidant for the oxidation of olefins is very challenging as it offers the utilization of waste and plentiful CO 2 together with the potential for the mitigation of its harmful environmental effect. Thus, this process is cost effective and environmentally challenging. Herein, we report the synthesis of a new crystalline porous organosilica material TSOS-1 with orthorhombic crystal structure by using a tailor made bridging organoslilane precursor prepared through the Schiff base condensation of p -terphenyl-4,4′'-dialdehyde and 3-aminopropyl-trimethoxysilane. This novel crystalline material TSOS-1 has been synthesized hydrothermally in the absence of any structure-directing agent and it showed high BET surface area (220 m 2 g −1 ) and nanoscale porosity. TSOS-1 is used as a support for stabilizing tiny AgNPs to obtain a robust nanocatalyst Ag@TSOS-1, which efficiently catalyses the conversion of styrene into predominantly styrene oxide (SO) using CO 2 as a soft oxidant in an autoclave reactor under mild reaction conditions.