Clip Chemistry to Create Hierarchically Porous Materials

I introduced semi-lability into MOFs and selectively cut the organic linkers inside the MOF to generate mesopores or even macropores that can accommodate large species, e.g., enzymes and nanoparticles. Linker instability, usually an undesirable trait of MOFs, was exploited to create mesopores by generating crystal defects throughout a microporous mixed-linker MOF crystal via thermolysis. Beside thermolysis, hydrolysis of chemically labile sites such as dynamic covalent bonds and photolysis of photosensitive linkers were investigated in MOFs. A sequential linker labilization and reinstallation method was used to expand the unit cell dimensions of MOFs while manipulating the framework structure and interpenetration. Gradual dissociation of the imine-based linkers and reinstallation of longer linkers into the defective spaces lead to the formation of non-interpenetrated isoreticular Zr-MOFs with progressively increased pore sizes. This work highlights new research opportunities by combining dynamic covalent chemistry with coordination chemistry in framework materials. In addition to the abovementioned examples based on labile covalent bonds in MOFs, I conducted more studies that demonstrate the role of the lability of coordination bonds in switching porosity insides MOFs. Linker migration triggered by desorption has been observed recently accompanied with a cascade lattice rearrangement in a defective Al-MOF. Spectroscopic measurements show that this counter-intuitive lattice rearrangement involves a metastable intermediate that results from solvent removal on coordinatively unsaturated metal sites. This disordered–crystalline switch between two topological distinct MOFs is shown to be reversible over four cycles through activation and reimmersion in polar solvents.

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Further reading:

  • Lo, S.-H.‡; Feng, L.‡; Tan, K.; Huang, Z.; Yuan, S.; Wang, K.; Li, B.-H.; Liu, W.-L.; Day, G. S.; Tao, S.; Yang, C.-C.; Luo, T.-T.; Lin, C.-H.; Wang, S.-L.; Billinge, S.; Lu, K.-L.; Chabal, Y.-J.; Zou, X.; Zhou, H.-C., Nat. Chem. 2020, 12, 90–97.

  • Feng, L.; Wang, K.-Y.; Day, G. S.; Ryder, M.; Zhou, H.-C., Chem. Rev. 2020, 120, 13087–13133.

  • Kirchon, A.‡; Feng, L.‡; Drake, H. F. ‡; Joseph, E. A.; Zhou, H.-C., Chem. Soc. Rev. 2018, 47, 8611–8638.

  • Feng, L.; Yuan, S.; Zhang, L.-L.; Tan, K.; Li, J.-L.; Kirchon, A.; Liu, L.-M., Zhang, P.; Han, Y.; Chabal, Y. J.; Zhou, H.-C., J. Am. Chem. Soc. 2018, 140, 2363–2372.

  • Feng, L.; Yuan, S.; Qin, J.-S.; Wang, Y.; Kirchon, A.; Qiu, D.; Cheng, L.; Madrahimov, S.; Zhou, H.-C., Matter, 2019, 1, 156–167.

  • Feng, L.‡; Lo, S.-H.‡; Tan, K.; Li, B.-H.; Yuan, S.; Lin, Y.-F.; Lin, C.-H.; Wang, S.-L.; Lu, K.-L.; Zhou, H.-C., Matter, 2020, 2, 988–999.

  • Feng, L.; Wang, K.-Y.; Lv, X.-L.; Yan, T.-H.; Zhou, H.-C., Nat. Sci. Rev. 2020, 7, 1743-1758.