Adsorption of Pb2+ on Rare-Earth benzene-1,3,5-tricarboxylate Metal-Organic Frameworks: Influence of the Crystal Structure and Size of Microcrystals

In this study, a series of rare-earth trimesates (REBTC, where RE3+ = La–Nd, Gd, Lu, and BTC3− = benzene-1,3,5-tricarboxylate, C6H3(COO−)3) was investigated for the removal of toxic Pb2+ ions from wastewater. The development of effective metal-organic frameworks (MOFs) for this purpose is an important challenge in environmental and materials science. The phase composition, crystal structure, and morphology of the samples have been characterized by powder X-ray diffraction, IR spectroscopy, TGA/DSC, and SEM. It has been established that the size of microcrystals has a decisive effect on the Pb2+ adsorption capacity. The LaBTC sample, with the composition [La(BTC)(H2O)6], the REBTC (Cc) structure type, and the smallest microcrystals, exhibited the best sorption performance, with a maximum adsorption capacity of 166.61 μmol/g, approximately 3–4 times that of GdBTC and LuBTC, which had larger microcrystals.