Global warming is an ever-rising environmental concern,
and carbon
dioxide (CO2) is among its major causes. Different technologies,
including adsorption, cryogenic separation, and sequestration, have
been developed for CO2separation and storage/utilization.
Among these, carbon capture using nano-adsorbents has the advantages
of excellent CO2separation and storage performance as
well as superior heat- and mass-transfer characteristics due to their
large surface area and pore volume. In this work, an environmentally
friendly, facile, bottom-up synthesis of ZIF-8 hollow nanospheres
(with reduced chemical consumption) was developed for selective CO2separation and storage. During this soft-templating synthesis,
a combined effect of ultra-sonication and low-temperature hydrothermal
synthesis showed better control over an oil-in-water microemulsion
formation and the subsequent growth of large-surface-area hollow ZIF-8
nanospheres having excellent particle size distribution. Systematic
studies on the synthesis parameters were also performed to achieve
fine-tuning of the ZIF-8 crystallinity, hollow structures, and sphere
size. The optimized hollow ZIF-8 nanosphere sample having uniform
size distribution exhibited remarkable CO2adsorption capability
(∼2.24 mmol g–1at 0 °C and 1.75 bar),
a CO2/N2separation selectivity of 12.15, a
good CO2storage capacity (1.5–1.75 wt %), and an
excellent cyclic adsorption/desorption performance (up to four CO2adsorption/desorption cycles) at 25 °C. In addition,
the samples showed exceptional structural stability with only ∼15%
of overall weight loss up to 600 °C under a nitrogen environment.
Therefore, the hollow ZIF-8 nanospheres as well as their highly controlled
soft-templating synthesis method reported in this work are useful
in the course of the development of nanomaterials with optimized properties
for future CO2capture technologies.