Stable Aluminum Metal-Organic Frameworks (Al-MOFs) for Balanced CO2 and Water Selectivity.

Three new Al-MOFs in the formation of [Al4(OH)2(OCH3)4(OH-BDC)3]·xH2O (BIT-72), [Al4(OH)2(OCH3)4(CH3-BDC)3]·xH2O (BIT-73) and {Al4(OH)2(OCH3)4[(CH3)2-BDC]3}·xH2O (BIT-74) have been synthesized by assembling Al3+ ion with terephthalic acid ions decorated with monohydroxyl, monomethyl or dimethyl groups, respectively. All of these three MOFs exhibit high stability in boiling water and acidic conditions. Among them, BIT-72 shows the highest surface area of 1618 m2·g-1 and IAST CO2/N2 selectivity of 48, while BIT-73 and BIT-74 present moderate IAST CO2/N2 selectivity and much lower H2O capacity below P/P0 = 0.3. The high CO2/N2 selectivity together with alleviative H2O sorption at low water relative pressure may provide promising potential in postcombustion CO2 capture.