Tunable Rare-Earth Metal-Organic Frameworks for Ultra-High Selenite Capture

Linkers and clusters with various conformations present challenges for the design and prediction of highly porous and stable rare-earth metal−organic frameworks (RE-MOFs), but provide great opportunities for the discovery of novel structures that enrich structural diversity. Herein, we designed and synthesized a series of RE-MOFs based on a malleable ligand to explore the effects of ligands, clusters, and configurations on structural stability. Under the low template concentration, two unstable (4,8)-connected hexanuclear UPC-181 with csq topology and UPC-182 with flu topology are formed. Interestingly, the auxiliary ligand participated in the purification and stabilization of UPC-182, affording (4,10)-connected UPC-182-BDC-R (R = H/NH2/NO2/OH/Br/ph) and UPC-182-FA. As the template concentration increases, the product is completely transformed from hexanuclear to nonanuclear, forming a highly stable (4,12)-connected UPC-183-RE (RE = Eu/Tb/Ho/Gd/Dy/Y) with shp topology. Due to the syngenetic effect of chemi- and physisorption, the adsorption capacity of UPC-183-Eu for selenite (SeO32- ) is as high as 568.04 mg/g, recorded one of the highest ever reported for MOFs. Furthermore, we accurately analyzed the adsorption site and energy of UPC-183-Eu for SeO32- through single-crystal structure and theoretical simulation. The ultra-high selenite adsorption capacity and removal efficiency endow UPC-183-Eu an excellent porous adsorbent for removing pollutants