Synthesis of Metal–Organic Framework Materials by Reflux: A Faster and Greener Pathway to Achieve Super-Hydrophobicity and Photocatalytic Application

In this contribution, reflux was demonstrated to be a faster and greener pathway in the synthesis of heterometallic metal–organic frameworks (MOFs) [Li2Sn2(BDC)3(H2O)2]n (LiSn; H2BDC = 1,4-benzenedicarboxylic acid). By means of this method, LiSn solid materials with various particle sizes and surface morphologies were achieved by simply changing the lithium sources (LiOH, 1, and LiNO3, 2). During the reflux process, the precursors were prone to grow from polyhedral LiSn materials, of which the LiOH was preferable to produce uniformly dispersed LiSn-1 nanoparticles with smaller sizes. These as-prepared LiSn materials possess good thermal stability proven by maintaining their structural crystallinity up to 250 °C. UV–vis diffuse reflectance spectroscopy suggested band gap energies (Eg) of 3.14 and 2.96 eV for LiSn-1 and LiSn-2, respectively, indicating the potential photocatalytic ability of these materials. Visible-light-driven degradation of methyl orange, methylene blue, and rhodamine B showing a higher photocatalytic performance in the presence of LiSn revealed high photocatalytic activity based on a first order kinetic study. Moreover, the LiSn-coated films resulted in the generation of hydrophobic substrate surfaces due to their specific hierarchy hills-and-valley type surface terrain with lotus leaf effects. Of special notice is the LiSn-1-coated stainless steel mesh and 200-mesh filter cloth showing magnificent oil–water separation property. This study discovered a family of bifunctional LiSn materials with both photocatalytic activity and super-hydrophobicity, showing great promise in water purification applications.