Engineering New Defects in MIL-100(Fe) via a Mixed-Ligand Approach To Effect Enhanced Volatile Organic Compound Adsorption Capacity

In the development of metal-organic frameworks (MOFs), expansion of pore size and exploration of facile preparation conditions are considered as two major goals that are rarely realized together. This study develops a facile method for the room-temperature synthesis of hierarchically porous MIL-100(Fe) under HF-free conditions using a mixed-ligand strategy by simultaneously introducing p-benzoquinone and terephthalic acid (TPA). The resulting MIL-100(Fe) products exhibited abundant micropores, large mesopores (similar to 40 nm) and macropores, and high stability, as revealed by N-2 adsorption-desorption isotherms, pore size distributions, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The synthesis mechanism of hierarchically porous MIL-100(Fe) elucidated that the introduced p-benzoquinone accelerated crystallization, while TPA generated crystal defects. The as-synthesized hierarchically porous MIL-100(Fe) acted as adsorbents with significantly improved performance than conventional MOFs and zeolites used for toluene and p-xylene adsorption. Furthermore, the adsorption behavior of toluene and p-xylene molecules in MIL-100(Fe) was investigated using molecular simulations. This simple and facile mixed-ligand method shows promise for the large-scale and low-cost production of various hierarchically porous MOFs in a wide range of applications.