Facile Aqueous Medium Synthesis of Highly Stable Zr-MOFs with Promising CO₂/CH₄ Adsorption Selectivity for Natural Gas and Biogas Upgradation

Abstract

Efficient CO2/CH4 separation is an important topic for the energy sector because of its implication in the economic upgradation of natural gas and biogas. Due to their excellent stability and high porosity, Zr-based MOFs are the best adsorbent candidates for targeted industrial applications through the adsorptive separation route. Herein, we report a scalable process for the synthesis of MOF-808(Zr) and DUT-67(Zr) analogues in aqueous solutions using zirconyl nitrate as a metal precursor and evaluate them as an adsorbent for CO2/CH4 separation. The as-synthesized materials were thoroughly characterized to verify the phase formation of the desired MOFs. They show similar porosity and stability to that obtained from conventional metal sources. Notably, at 298 K, the CO2 sorption analysis of MOF-808@N shows a relatively high uptake of 5.6 mmol/g at 10 bar. The CO2/CH4 selectivity in the same conditions for a 50:50 v/v binary mixture is 9.2, higher than that of well-known reported MOF adsorbents. The excellent separation performance was attributed to the large micropore volume and defect sites in the MOF framework. This study suggests that zirconyl nitrate could be an effective metal salt precursor for synthesizing Zr-MOFs for natural gas and biogas upgrading.