The Functionalization of MOF-5 with Hexamethylenetetramine for CO2 Capture /

Abstract

This study demonstrates that the synthesis of HMTA-modified Zn BDC and Ni BDC metal-organic frameworks leads to materials exhibiting superior structural properties and increased capacities for CO2 adsorption. The integration of HMTA enhances the surface area and markedly improves the efficiency of these metal-organic frameworks (MOFs) in CO2 capture, thereby establishing them as viable options for gas separation and environmental remediation applications. The Zn BDC and Ni BDC metal-organic frameworks (MOFs), along with their corresponding HMTA-modified variants, Zn BDC⊃HMTA and Ni BDC⊃HMTA are prepared through hydrothermal method. The synthesized metal-organic frameworks (MOFs) were characterized through a range of analytical techniques, which encompassed X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) analysis. The XRD and SEM analysis demonstrated a crystal structure with notable morphological variations, suggesting that the inclusion of HMTA transformed the structure from irregular microspheres to interconnected sheets. The BET analysis revealed that the surface areas for Zn BDC⊃HMTA and Ni BDC⊃HMTA were significantly enhanced, measuring 66.53 m²/g and 220.91 m²/g, respectively, in comparison to their non-HMTA counterparts. The evaluation of CO2 adsorption capacities measured by utilizing a high-pressure gas sorption analyzer demonstrated that the HMTA-modified MOFs displayed enhanced CO2 adsorption properties, with Zn BDC⊃HMTA reaching a peak adsorption capacity of 3.50 mmol/g at 283 K, whereas Ni BDC⊃HMTA exhibited an adsorption capacity of 2.85 mmol/g. Both the values are higher than the unmodified BDC based MOFs. The results underscore the efficacy of HMTA as a modifying linker, significantly improving both the surface area and the adsorption capabilities of the metal-organic frameworks (MOFs).