Mechanical compression-induced shaping of zinc triazolate oxalate CALF-20 for CO2 capture

Abstract

The escalating intensification of CO₂ emissions, coupled with their direct influence on climate change due to the greenhouse effect, epitomizes urgent environmental issues demanding immediate intervention. CALF-20, a Zn-triazolate-based Metal-Organic Framework (MOF), exhibits considerable potential in applications designed for CO₂ adsorptive capture. Within this study, CALF-20 powder was synthesized and shaped into pellets through a mechanical compression method, implemented both independently and in conjunction with a binder. The pellets were subsequently subjected to characterization via XRD, PXRD, SEM, N₂ adsorption, FTIR, and TGA analyses. The mechanical robustness and CO₂ adsorption capacity of various samples were evaluated. The CO₂ adsorption kinetics of selected CALF-20 pellets were scrutinized utilizing pseudo-first order, pseudo-second order, and Avrami's kinetic models. Concurrently, the rate-limiting step was determined through Boyd's film diffusion, interparticle diffusion, and intraparticle diffusion models. The results disclosed that mechanical compaction at 10 tons could amplify the mechanical strength of CALF-20–45.61 N. Additionally, the integration of 12.5 wt% Polysulfone (PSU) as a binder augmented the mechanical strength of CALF-20 pellets to 204.94 N. The introduction of PSU not only fortified the mechanical resilience of the pellets but also mitigated the deterioration of CO₂ adsorption capacity induced by compression. Following this, the performance of CALF-20 pellets under diverse CO₂ concentrations and adsorption temperatures was appraised, and their recyclability under N₂ or CO₂ regeneration atmospheres was probed. This study introduces a promising approach for the creation of stable and structured MOFs, specifically designed for CO₂ removal applications.