Multifunctional Zn-MOF-74 as the gas adsorbent and photocatalyst

Van Thi Thuy Nguyen, Cam Loc Luu, Tri Nguyen, Anh Phung Nguyen, Cuong Tien Hoang and Anh Cam Ha

Abstract

Zn-MOF-74 framework of needle-like shape crystal of 2.5–10 μm in diameter and 30–80 μm in length had been successfully synthesised by solvothermal method. The obtained material was characterised by several techniques, including x-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV–vis). The greenhouse gases uptake of the Zn-MOF-74 was studied by isothermal adsorption method at 30 °C and pressure from 1 to 30 bars. The activity for photo-removement of glyphosate (GLP) solution and gas phase p-xylene was tested on Zn-MOF-74 powder and thin film from Zn-MOF-74 + TiO₂ P25 mixture, respectively, at ambient condition. Possessing high surface area up to 826 m² g⁻¹, micropore volume of 0.344 cm³ g⁻¹, thermal stability up to 401 °C, and low band gap energy (2.09 eV), synthesised micropore Zn-MOF-74 was proven to be highly active visible-light photocatalyst and a potential adsorbent for greenhouse gases. As it followed from investigation, Zn-MOF-74 has adsorption capacity of 122.43 cm³ g^–1 and 202.52 cm³ g⁻¹ at 30 bars, respectively, for CH₄ and CO₂. As a visible-light photocatalyst, Zn-MOF-74 removed 75% GLP for 90 min and 1.25 g_xyl g⁻¹ _cat of p-xylene for 60 min under UV–vis irradiation at ambient condition.