Modulated Hydrothermal Chemistry of Metal–Organic Frameworks

Conspectus Metal–organic frameworks (MOFs) are infinite networks composed of inorganic metals and organic linkers, and have demonstrated superior advantages over traditional porous materials in gas storage, separation, catalysis, etc., because of possessing ultrahigh surface areas and tunability in pore sizes, topologies, shapes, and functionalities. Although tremendous progress has been made in the fundamental research and applications of MOFs, developing a green and large-scale approach to synthesizing MOFs with repeatably high quality remains a key step for their massive production and industrial applications. Traditional solvothermal and hydrothermal approaches usually synthesize MOFs on a small scale with challenges in quality control. In addition, these synthetic processes typically require high temperatures, high pressures, and sometimes large amounts of environmentally unfriendly organic solvents. In this Account, we elaborate on the recent progress of the modulated hydrothermal (MHT) chemistry developed by us, which helps synthesize zirconium/hafnium-based MOFs in green (aqueous solutions), mild (≤120 °C, 1 atm), and scalable fashion. The MHT chemistry has already served as a solid foundation for the design and scale-up synthesis of multifunctional MOF materials by tuning the types and concentrations of ligands and modulators and their ratios. It not only applies to the classical UiO-66-type and MOF-808-type MOFs, but also suits the design of new MOFs, such as NUS-6, NUS-8, and NUS-36. In addition, the MHT-enabled MOFs have demonstrated promising applications in gas separation and storage, Lewis/Brønsted acid-catalyzed oxidation reactions/biomass conversion, and piezoelectric/ferroelectric devices. This Account further prospects the evolution of MHT chemistry in developing new functional MOFs composed of different metals, such as titanium, zirconium, hafnium, cerium(IV), etc., on a large scale and sustainable paradigm.