Decoupling microporosity and nitrogen content to optimise CO2 adsorption in modified xerogels

Selected melamine-resorcinol-formaldehyde (MRF) xerogels have been synthesised and analysed to determine the influence of nitrogen (N) incorporated into the gel structure, as well as, resorcinol to catalyst (sodium carbonate) and resorcinol to formaldehyde molar ratios. The aforementioned factors were varied, and their effect on gel properties characterised, allowing a better understanding of how gel characteristics can be tailored, and their impact on gel performance. MRF gels, produced in this study, were characterised using volumetric and gravimetric analyses to determine porous structure and quantify CO2 capture capacities and kinetics, as well as allowing determination of heats of adsorption and activation energies for CO2. MRF10_200_0.25 has exhibited the largest CO2 capacity (1.8mmol/g at 0 °C) of the sample tested. Thermal stability was tested by proximate analysis, and MRF xerogels exhibited high thermal stability, however it was found that volatile matter increases as [M] increases, particularly for [M] 20%w/w and higher. Working capacity was determined from a series of cycling studies and capacities of 0.55, 0.58 and 0.56 mmol/g at 60 °C were observed for [M] of 10, 20 and 30%w/w, respectively. The measured heat of adsorption showed that incorporation of nitrogen functionalities results in a low energy penalty demonstrating that the adsorption mechanism is still driven by physical forces. The results obtained indicate that the family of materials studied here offer potential routes for carbon capture materials, through a combination of micropore structure development and incorporation of favourable Lewis acid-base interactions.