Elucidating Improvements to MIL-101(Cr)'s Porosity and Particle Size Distributions based on Innovations and Fine-Tuning in Synthesis Procedures

Among the existing metal-organic frameworks (MOFs), MIL-101(Cr) is renowned for its stability in air and water. As a result, MIL-101(Cr) has numerous potential applications ranging from adsorptive cooling to catalysis. The industrial-scale production of MIL-101(Cr) is necessary before realizing these applications. Yet, there remain two main bottlenecks in preparing MIL-101(Cr) in bulk: the toxicity of hydrofluoric acid (HF) used in conventional MIL-101(Cr) synthesis and the challenge of ensuring that the as-prepared MIL-101(Cr) is highly porous with specific Brunauer-Emmett-Teller surface area (S-BET) above 4000 m(2) g(-1). On the laboratory scale, MIL-101(Cr) often presents S-BET 2300-3500 m(2) g(-1). The synthesis and purification procedures often influence the yield, particle size, porosity, and other properties of MIL-101(Cr). This critical review examines trends in MIL-101(Cr) preparation procedures and the MOF's resulting properties to elucidate areas for improvement toward its real-world applications. The purification processes for conventional HF-based MIL-101(Cr) whereby porosities vary despite the same synthesis approach are first investigated. Next, the reported additives for substituting HF and their influence on the resulting MIL-101(Cr)'s porosity and particle size are discussed. The selection of additives may be application-specific: exemplified in the examination of MIL-101(Cr)'s preparation, its corresponding water sorption capacity, and desiccant-related applications.