Hollow metal-organic frameworks (MOFs) are promising materials with sophisticated structures, such as multiple shells, that cannot only enhance the properties of MOFs but also endow them with new functions. Herein, we show a rational strategy to fabricate multi-shelled hollow chromium (III) terephthalate MOFs (MIL-101) with single-crystalline shells through step-by-step crystal growth and subsequent etching processes. This strategy relies on the creation of inhomogeneous MOF crystals in which the outer layer is chemically more robust than the inner layer and can be selectively etched by acetic acid. The regulation of MOF nucleation and crystallization allows the tailoring of the cavity size and shell thickness of each layer. The resultant multi-shelled hollow MIL-101 crystals show significantly enhanced catalytic activity during styrene oxidation. The insight gained from this systematic study will aid in the rational design and synthesis of other multi-shelled hollow structures and the further expansion of their applications.
In traditional steam reforming of CH 4 , the CH 4 conversion and its selectivity to CO and H 2 are thermodynamically limited. In this work, we designed a series of Ni−Fe redox catalysts with varying Ni/Fe ratios. The Ni−Fe redox catalysts could function as oxygen carriers to selectively convert CH 4 to syngas via chemical looping. The selectivity to CO was dramatically enhanced via a selective conversion route of CH 4 to C and H 2 in the reduction, followed by C gasification to syngas with hot steam. Taking the advantages of the highly reactive Ni species for CH 4 activation and Fe species for water splitting, together with the resulting NiFe alloy in the reduced catalyst for catalytic CH 4 decomposition, high CH 4 conversion up to 97.5% and CO selectivity up to 92.9% were achieved at 900 °C with productivity of CO and H 2 of 9.6 and 29.0 mol kg catalyst −1 , respectively, on equimolar Ni−Fe catalyst.
Hollow metal–organic frameworks (MOFs) are promising materials with sophisticated structures, such as multiple shells, that cannot only enhance the properties of MOFs but also endow them with new functions. Herein, we show a rational strategy to fabricate multi‐shelled hollow chromium (III) terephthalate MOFs (MIL‐101) with single‐crystalline shells through step‐by‐step crystal growth and subsequent etching processes. This strategy relies on the creation of inhomogeneous MOF crystals in which the outer layer is chemically more robust than the inner layer and can be selectively etched by acetic acid. The regulation of MOF nucleation and crystallization allows the tailoring of the cavity size and shell thickness of each layer. The resultant multi‐shelled hollow MIL‐101 crystals show significantly enhanced catalytic activity during styrene oxidation. The insight gained from this systematic study will aid in the rational design and synthesis of other multi‐shelled hollow structures and the further expansion of their applications.
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