The catalytic activity of metal–organic frameworks (MOFs) depends largely on the presence of structural defects. In the present study, cobalt based metal–organic framework TMU-10, [Co₆(oba)₅(OH)₂(H₂O)₂(DMF)₄]_n·2DMF has been subjected to controlled thermolysis under air atmosphere at different temperatures in the range of 100–700 °C. This treatment results in the removal of ligands, and generation of structural defects and additional porosity in a controlled manner. The resulting materials, denoted as quasi MOFs according to the literature, were subsequently employed as catalysts for hydrogen release from NaBH₄ by hydrolysis. The quasi TMU-10 framework obtained at 300 °C (QT-300) shows the highest turnover frequency of the series with a value of 13 333 mL min⁻¹ g⁻¹ at room temperature in the absence of a base, with an activation energy of 56.8 kJ mol⁻¹. The simultaneous presence of micro- and mesopores in QT-300 with unsaturated Lewis acid sites on cobalt nodes due to the conversion of a fraction of Co(II) centers to Co(III) as well as the presence of tetrahedral Co(II) sites is responsible for this catalytic behavior. The influence of the catalyst dosage and BH₄⁻ concentration is in good agreement with the Langmuir–Hinshelwood model in which both reactants must be adsorbed onto the catalyst surface. Further investigation on the hydrolysis of the NaBH₄ + D₂O system presents a primary kinetic isotope effect indicating that water O–H bond cleavage occurs in the rate determining step.

中文翻译：

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通过后合成孔工程制备的准 MOFs 具有高氢释放催化活性

金属有机骨架（MOF）的催化活性很大程度上取决于结构缺陷的存在。在本研究中，钴基金属有机骨架 TMU-10、[Co ₆ (oba) ₅ (OH) ₂ (H ₂ O) ₂ (DMF) ₄ ] _n ·2DMF 在100–700 °C 范围内的不同温度。这种处理导致配体的去除，并以受控方式产生结构缺陷和额外的孔隙率。所得材料根据文献表示为准 MOF，随后用作从 NaBH _{4 中}释放氢的催化剂通过水解。在 300 °C (QT-300) 下获得的准 TMU-10 框架显示出该系列的最高周转频率，在室温下，在没有碱的情况下，其值为 13 333 mL min ^-1 g ^-1，具有激活56.8 kJ mol ^{-1 的}能量。由于部分 Co( II ) 中心转化为 Co( III ) 以及四面体 Co( II ) 位点的存在，QT-300 中同时存在微孔和中孔，在钴节点上具有不饱和路易斯酸位点负责这种催化行为。催化剂用量和 BH ₄ ^{- 的影响}浓度与 Langmuir-Hinshelwood 模型非常吻合，其中两种反应物都必须吸附到催化剂表面。对 NaBH ₄ + D ₂ O 系统水解的进一步研究显示了主要的动力学同位素效应，表明水的 O-H 键断裂发生在速率确定步骤中。