Synthesis, characterization and hygrothermal behaviour of mesoporous silica high-performance desiccants for relative humidity buffering in closed environments

Four different mesoporous silica (MS) samples were synthesized for assessment as candidate rapid-response desiccant materials. Their behaviour was compared with that of conventional desiccants. The aim was to enable tuning of hygrothermal functional behaviour by correlating this with microstructural composition. Pore geometry was characterized and validated using small-angle X-ray diffraction, Brunauer–Emmett–Teller analysis, Barrett–Joyner–Halenda analysis and high-resolution transmission electron microscopy. The volume and mean diameter of the mesopore network are directly related, and when increased cause a proportional decrease in macropore volume and bulk porosity, suggesting that the pore wall thickness decreases at larger mesopore volumes. Thermophysical properties were characterized using modified transient plane source and differential scanning calorimetry. Vapour storage and sorption/desorption response rates were characterized using modified dynamic vapour sorption (DVS) techniques. The DVS response time, temc, has a positive logarithmic relationship with both mesopore diameter and mesopore volume, whilst vapour permeance appears to be inversely related. All MS samples had a significantly higher vapour storage capacity and quicker DVS response rate than the conventional desiccants, including silica gel, zeolite, molecular sieve and bentonite.