Synthesis of ultramicroporous zeolitic imidazolate framework ZIF-8 via solid state method using a minimum amount of deionized water for high greenhouse gas adsorption: A computational modeling

It is widely recognized that greenhouse gas emissions (e.g., CO2, SF6, and CH4) play a significant role in global warming. Adsorption at point sources, using a suitable adsorbent, is an important method to reduce their release. Zn(mIm)2, where mIm = 2-methylimidazolate (referred to as SOD-ZIF-8), is a typical Zeolitic Imidazolate Framework (ZIF) that has shown outstanding performance in the adsorption of greenhouse gases. However, its conventional synthesis is time-consuming and requires the addition of large amounts of organic solvents. Herein, we report a solid -state synthesis of ultramicroporous n-ZIF-8 nanocrystals at room temperature within 5 min. The comprehensive characterization of n-ZIF-8 involved FTIR, XRD, SEM, TGA analyses, and N2 adsorption. The obtained results indicate that n-ZIF-8 has potential as an adsorbent for greenhouse gas adsorption. The physisorption process of CO2, SF6, and CH4 is corroborated by the isosteric heat of adsorption (Qads) data. To further support the experimental data, quantum computational DFT-GD3 calculations were performed. Validation by the quantum theory of molecules (QTAIM) confirms that the selected gases are well adsorbed through major electrostatic interactions. Additional support from the 3D-ELF/2D-LOL analyses, agreeing with QTAIM claims, highlights that ZIF-8 highly adsorbs CO2 and CH4 through van der Waals interactions. In conclusion, ZIF-8 exhibits remarkable adsorption capabilities, efficiently adsorbing CO2 in the cavity and N2 on the surface, making it a potential candidate for greenhouse gas removal.