A robust photo-responsive zirconium metal-organic framework for tailorable CO₂ capture

Photo-responsive adsorbents (PRAs) have attracted much attention due to their energy efficiency for controllable gas capture. However, the construction of robust PRAs is still full of challenges. In this project, we report the construction of azobenzene-modified UiO-67, namely Azo-U, consisted of hexa-nuclear zirconium clusters and azobenzene derivative ligand Azo-H₂BPDC. The single crystal X-ray diffraction (SCXRD) analysis demonstrates that Azo-U shows analogous structures to UiO-67 and the specific surface area is up to 1327 m²·g⁻¹ derived from N₂ uptake property at 77 K. The incorporation of Azo-H₂BPDC imparts Azo-U with reversible photo-responsive properties. Considering its high porosity and photo-responsive properties, Azo-U was evaluated for controllable CO₂ capture and the regulation efficiency can be up to 25.5%. Such a photo-controllable CO₂ capacity of Azo-U is further confirmed by density functional theory (DFT) and Grand Canonical Monte Carlo calculation. Besides, the regulation efficiency can be well-preserved upon alternative ultraviolet and visible light irradiation. Moreover, Azo-U possesses good stability under aqueous solutions of different pH values (1.0 to 11.0). This study might shed light on the design and fabrication of target-specific PRAs to meet the various demands.