Four new Al-based microporous metal-organic framework compounds with MIL-53-type structure containing functionalized extended linker molecules

Abstract Al-based metal-organic framework (MOF) compounds containing nitro- and amino-substituted and sulfone-bridged groups were synthesized: [Al(OH)(NDC-(NO 2 ) 2 )] ( 1 ), [Al(OH)(BPDC-NO 2 )] ( 2 ), [Al(OH)(BPDC-NH 2 )] ( 3 ) and [Al(OH)(BPDC-SO 2 )] ( 4 ), which are analogs of MIL-69/DUT-4 ([Al(OH)(NDC)]) or DUT-5 ([Al(OH)(BPDC)]) (NDC = 2,6-naphthalenedicarboxylate, BPDC = 4,4’-biphenyldicarboxylate). The compounds were synthesized under solvothermal conditions employing microwave-assisted heating and characterized by powder X-ray diffraction, thermogravimetric analysis and gas sorption measurements. They exhibit permanent porosity and are accessible to carbon dioxide, hydrogen and methane but do not show any framework flexibility like MIL-53. All compounds are highly stable as confirmed by temperature-dependent powder X-ray diffraction measurements (TD-PXRD) and framework decomposition takes place between 340 °C and 420 °C.