Cobalt-Atom Active Sites Grafted UiO-66-NH2 via EDTA for the Enhanced Production of Syngas in CO2 Photoreduction

Abstract

In recent years, the use of photocatalysts has emerged as a promising research direction to transform harmful CO₂ molecules into renewable fuels. In this work, the chelating agent ethylenediaminetetraacetic acid (EDTA) containing a central metal atom like Co was attached to the UiO-66-NH₂ metal–organic frameworks (MOFs) through a one-pot synthesis. Several samples with different molar ratios of UiO-66-NH₂–Co and EDTA (molar ratios of UiO-66-NH₂–Co/EDTA is 1.2; 0.6; and 0.4) were synthesized and assessed for photocatalytic CO₂ reduction to produce syngas (the mixture of CO and H₂), which can be used for generating liquid fuels. Among these samples, the highest syngas production rate was achieved by sample U-E-0.6, yielding around 776.40 and 1217.29 μmol g^–1 h^–1 of CO and H₂, respectively, at the end of 4 h. Multiple investigations, including electrochemical impedance, time-resolved, steady state photoluminescence, linear sweep voltammetry, and photocurrent measurements, revealed that the addition of EDTA-metal to UiO-66-NH₂ improved the photoelectrochemical properties of the system, thereby enhancing its photocatalytic activity under solar irradiation. This research paves the way for the development of a single atom encapsulated in the MOF material for photocatalytic CO₂ reduction.