Assembly of Solvent-Incorporated Rod Secondary Building Units to Ultramicroporous Metal–Organic Frameworks for Acetylene Purification

The process of industrial purification of acetylene (C2H2) is crucial yet challenging due to the similarities in physical properties and kinetic molecular sizes between C2H2 and the impurity gases generated during its production. Conventional distillation processes frequently result in significant energy waste, highlighting the urgent need for more efficient separation techniques. Metal–organic frameworks (MOFs), as a class of porous physical adsorbents, have demonstrated remarkable success in the separation and purification of light hydrocarbons. By applying the reticular chemistry approach, we have rationally designed and synthesized two isoreticular compounds (named CoTPTA and MnTPTA) with novel low-valent {M–O–M} rod secondary building units (SBUs) based on the tetracarboxylic acid ligand H4TPTA ([1,1′:3′,1″-terphenyl]-4,4′,4″,6′-tetracarboxylic acid). Both compounds displayed outstanding chemical stability when exposed to various organic solvents. In addition, a series of gas adsorption experiments demonstrated that they both have good C2H2 purification ability. The adsorption selectivity was subsequently verified by ideal adsorption solution theory (IAST), where the selectivity of CoTPTA for C2H2/CO2 was 6.65 (v/v = 0.5:0.5).