Enhancing the Catalytic Activity of MOF‐808 Towards Peptide Bond Hydrolysis through Synthetic Modulations

Abstract

The performance of MOFs in catalysis is largely derived from structural features, and much work has focused on introducing structural changes such as defects or ligand functionalisation to boost the reactivity of the MOF. However, the effects of different parameters chosen for the synthesis on the catalytic reactivity of the resulting MOF remains poorly understood. Here, we evaluate the role of metal precursor on the reactivity of Zr-based MOF-808 towards hydrolysis of the peptide bond in the glycylglycine model substrate. In addition, the effect of synthesis temperature and duration has been investigated. Surprisingly, the metal precursor was found to have a large influence on the reactivity of the MOF, surpassing the effect of particle size or number of defects. Additionally, we show that by careful selection of the Zr-salt precursor and temperature used in MOF syntheses, equally active MOF catalysts could be obtained after a 20 minute synthesis compared to 24 h synthesis.

Understanding the Role of Surfactants in the Interaction and Hydrolysis of Myoglobin by Zr‐MOF‐808

“…N 2 isotherms (Figure S1) indicated formation of a microporous MOF material with moderate surface area of 1072 m 2 /g, with well defined pores of 6.65 Å and 18.44 Å, in agreement with previous reports [31,35] . The presence of an additional pore at 9 Å suggests that defects are present within the crystal structure.…”

“…N 2 isotherms (Figure S1) indicated formation of a microporous MOF material with moderate surface area of 1072 m 2 /g, with well defined pores of 6.65 Å and 18.44 Å, in agreement with previous reports. [31,35] The presence of an additional pore at 9 Å suggests that defects are present within the crystal structure. As no C=O stretch at 1700 cm À 1 was present in the FT-IR spectra after MOF activation (Figure S2), the presence of missing clusters was ruled out, and defects were determined to be missing linker defects.…”

Zirconium oxo clusters as discrete molecular catalysts for the direct amide bond formation

“…[54][55][56] However, further design of these catalysts is not yet a simple task. The heterogeneous nature of Zr-MOFs, and the variability on the structure arising from different synthesis protocols 57 makes it challenging to obtain detailed molecular insights on the catalytic activity, despite important advances in the area. [58][59][60][61] Similarly, most Zr/ Hf-polyoxometalate complexes active as Lewis acid catalysts usually feature a single catalytic active Zr/Hf center, 53 and precisely engineering novel POM structures is not yet a straightforward endeavor.…”

Dynamic environment at the Zr6 oxo cluster surface is key for the catalytic formation of amide bonds

“…[6][7][8][9] Notably, several Zr-MOFs feature catalytic active metal sites in their Zr 6 O 8 cluster nodes, either intrinsically or due to missing linker defects. 8,[10][11][12] In our work, we have leveraged these active sites to develop novel classes of metal oxo cluster based catalysts for the cleavage, 9,[13][14][15][16][17][18][19] or formation 20 of amide bonds with a unique tolerance to the water formed during the reaction. [21][22][23] Recently, we have also showcased that zirconium oxo clusters (ZrOC) can be used as discrete molecular catalysts.…”