Optimizing Fe‐Based Metal‐Organic Frameworks through Ligand Conformation Regulation for Efficient Dye Adsorption and C 2 H 2 /CO 2 Separation

Regulating the structure of metal‐organic frameworks (MOFs) by adjusting the ligands reasonably is expected to enhance the interaction of MOFs on special molecules/ions, which has significant application value for the selective adsorption of guest molecules. Herein, two tricarboxylic ligands H 3 L−Cl and H 3 L−NH 2 were designed and synthesized based on the ligand H 3 TTCA by replacing part of the benzene rings with C=C bonds and modifying the chlorine and amino groups on the 4‐position of the benzene ring. Two 3D Fe‐MOFs ( UPC‐60‐Cl and UPC‐60‐NH 2 ) with the new topology types were constructed. As the C=C bonds of the ligands have flexible torsion angles, UPC‐60‐Cl features three types of irregular 2D channels, while UPC‐60‐NH 2 has a cage with two types of windows on the surface. The synergistic effect of unique channels and modification of functional groups endows UPC‐60‐Cl and UPC‐60‐NH 2 with high adsorption capacity for organic dyes. Compound UPC‐60‐Cl shows high adsorption capacity for CV (147.2 mg g −1 ), RHB (100.3 mg g −1 ), and MO (220.9 mg g −1 ), whereas UPC‐60‐NH 2 exhibits selective adsorption of MO (158.7 mg g −1 ). Meanwhile, based on the diverse pore structure and modification of active sites, UPC‐60‐Cl and UPC‐60‐NH 2 show the selective separation of equimolar C 2 H 2 /CO 2 . Therefore, reasonable regulation of organic ligands plays a significant role in guiding the structure diversification and performance improvement of MOFs.