Investigation of the Off-Target Synthesis of a Bromide-Carrier Amorphous Aluminosilicate Geopolymer (GP-97d500) as an Environmentally Benign Material: Thermodynamic and CO₂ Adsorption Mechanism at Ambient Temperature

Unlocking the potential of a CO2 porous sorbent that is simple to use, economical, has high adsorption capacity, and stable performance has drawn consideration among researchers. In this study, we present off-target synthesis of TUN zeolite, confirmed as an amorphous aluminosilicate CO2 geopolymer sorbent with the NaBr secondary phase remaining (labeled as GP-97d500). It features a viable, easily synthesized, low-cost, and environmentally benign material with respectable CO2 capture capacity of up to 2.37 mmol/g (25 °C, 0.979 bar) and reached a maximum of 3.60 mmol/g (0 °C, 0.979 bar). The structural integrity, sub-micron crystal morphology, and particle size characteristics were verified using XRD, SEM-EDS, and PSD metrics. Textural properties were mapped via N₂ physisorption alongside Density Functional Theory (DFT). This exceptional ambient performance was justified by calculating the Isosteric Heat of Adsorption (Qst) profiles from the Clausius-Clapeyron equation. Qst values are ≤40 kJ/mol, indicating dominant physisorption for the entire process.