The impact of binders on magnetic framework composite pellets for CO2 capture

Abstract

Magnetic framework composites (MFCs), comprising magnetic nanoparticles (MNPs) embedded in metal–organic frameworks (MOFs), have emerged as an exciting novel class of advanced functional materials. MFCs show particular promise for CO₂ capture, where they overcome the low thermal conductivity barriers of MOFs by facilitating the use of magnetic induction heating for thermal regeneration. Current research in the field has focussed on dry powder MFCs. However, for scale up towards use in industry, these powders require formulating into larger structures such as pellets. Herein we present the first study of pelletisation routes for MFCs.

MFCs were first produced via an innovative continuous flow synthesis with multiple concentrations of magnetic nanoparticles, then formulated into pellets with various polymer binders. Surface area and CO₂ capacity losses caused by pelletisation were minimised using a low-pressure extruder, with some binders showing zero pore blocking effects. Pellet mechanical strength was increased by 107% (crushing load) and 87% (elastic modulus) from formulating with just 4% polyvinyl alcohol binder. We also present the first investigation into the thermal properties of MFCs, essential for modelling the materials’ behaviours in packed bed adsorbers. Notably, thermal conductivity increased by 47% with 7.8% MNPs in the MFCs, compared to the pristine MOF, highly beneficial for applications requiring thermal cycling. The formulation and pelletisation methods explored are applicable to a range of MOFs and MFCs, facilitating the shaping of these exciting materials for positive impact across CO₂ capture and other applications.