The reaction between 1,3,5-benzenetribenzoic acid (H3BTB) and In(NO3)3 hydrate in diethylformamide yielded a new InIII-metal-organic framework, [(CH3CH2)2NH2]3[In3(BTB)4]·10DEF·14H2O (I). The countercation and solvent-free doubly interpenetrated I potentially contains 71.0% of solvent accessible void. Although the framework of I was not stable enough to maintain its original structure when the solvent molecules were removed, the as-prepared I was found to be a very good sorbent for acridine orange hydrochloride, a large Reichardt's dye, and hydrophobic iodine molecule in solution. The as-prepared I exhibited increased uptake amount in the order of Reichardt's dye > acridine orange hydrochloride > iodine. The largest uptake of the bulky Reichardt's dye by I could be attributed to the optimized structural fitting of Reichardt's dye into the large three-dimensional void space of I. The structure of Reichardt's dye-encapsulated I-RD was unambiguously revealed by X-ray crystallography for the first time.