A nitro-decorated MOF is used for the selective separation of benzene and cyclohexane in both liquid and vapor phases.

Separation of hydrocarbon molecules, such as benzene/cyclohexane and o-xylene/m-xylene/p-xylene, is relevant due to their widespread application as chemical feedstock but challenging because of their similar boiling points and close molecular sizes. Physisorption separation could offer an energy-efficient solution to this problem, but the design and synthesis of sorbents that exhibit high selectivity for one of the hydrocarbons remain a largely unmet challenge. Herein, we report a new heterometallic MOF with a unique tortuous shape of channels decorated with aromatic sorption sites [Li2Zn2(bpy)­(ndc)3] (NIIC-30­(Ph), bpy = 4,4′-bipyridine, ndc2– = naphthalene-1,4-dicarboxylate) and study of its benzene/cyclohexane and xylene vapor and liquid separation. For an equimolar benzene/cyclohexane mixture, it is possible to achieve a 10-fold excess of benzene in the adsorbed phase. In the case of xylenes, microporous framework NIIC-30­(Ph) demonstrates outstanding selective sorption properties and becomes a new benchmark for m-/o-xylene separation. In addition, NIIC-30­(Ph) is stable enough to carry out at least three separation cycles of benzene/cyclohexane mixtures or ternary o-xylene/m-xylene/p-xylene mixtures both in the liquid and in the vapor phase. Insights into the performance of NIIC-30­(Ph) are gained from X-ray structural studies of each aromatic guest inclusion compound.

Two solvent-controlled topological isomers of scandium-organic frameworks [Sc(Hpzc)) were synthesized using 2,5-pyrazinedicarboxylate. Despite the isomeric nature of the obtained MOFs they possess different structural features and unique adsorption properties towards gases and iodine. The compound 1 has widely spread among MOF's structures dia topology with ultra-narrow channels which together with inner surface functionalization leads to enhanced CO2 adsorption and high selectivity factors in CO2/CH4 and CO2/N2 gas mixtures (25.9 and 35.6, respectively, 1/1 v/v). Moreover, rare preferable adsorption of CO2 over C2H2 was demonstrated. The biporous isomeric framework 2 has crb topology inherent in zeolites. Remarkable adsorption affinity to C2H2 with the IAST selectivity factor of 127.1 for C2H2/C2H4 mixture (1/99 v/v) was achieved for 2. Both compounds have exceptional chemical stability in a wide range of pH from acidic to basic media.