Room-temperature aqueous synthesis of MOF-808(Zr) for selective adsorption of dye mixtures

Abstract

ZrIV-based metal–organic frameworks (MOFs) featuring distinguished water stability, large surface area, and intriguing functionalities have immense potential for practical usage. However, conventional MOF synthesis approaches generally require high reaction temperatures and organic solvents to initiate and template the nucleation and growth, hindering sustainable and cost-effective manufacturing and application of Zr-based MOFs. In this study, a scalable, room-temperature and aqueous synthesis of MOF-808—a Zr-MOF extensively explored as an adsorbent in both academic and industrial sectors—was reported. A rational use of water/formic acid (FA) as a green co-solvent enabled the formation of Zr6-cluster in an aqueous phase, thereby facilitating subsequent coordination with H3BTC to yield well-crystallized MOF-808. The effects of the water/FA volume ratio, the total solvent volume, and reaction time on the physicochemical properties of MOF-808 were studied. The optimized synthesis conditions (FA/water = 2.7:8.1, and reaction time = 24 h) resulted in the synthesis of MOF-808 with good hydrophilicity, excellent stability, high surface area, and weak positive charges. Moreover, this synthesis approach was successfully upscaled, yielding 11.5 g of MOF-808 at a magnification factor of 48. Notably, MOF-808-V10.8 exhibited an impressive adsorption capacity for Congo Red (ca. 1500 mg/g) and demonstrated selective fractionation of dye mixtures, suggesting their potential application in dye wastewater treatment. This methodology is expected to provide guidance for aqueous and scalable fabrication of Zr-MOFs towards water-related environmental applications.