Effect of linker hybridization on the wetting of hydrophobic metal-organic frameworks
Eder Amayuelas, Sandeep Kumar Sharma, Jaideep Mor, Luis Bartolomé, Liam J. W. Johnson, Davide Caporale, Andrea Le Donne, Gianmarco Sigolo, Łukasz Scheller, Viviana Cristiglio, P. Zajdel, Simone Meloni, Yaroslav Grosu
Abstract
Wetting-dewetting of nanoporous materials is of key importance for a wide range of natural and technological cases, which include separation, chromatography, ionic channels. Heterogeneous lyophobic systems (HLS) consisting of a lyophobic nanoporous material and a non-wetting liquid are attractive for thermomechanical energy storage, conversion and dissipation under pressure/temperature variations. In recent years, metal-organic frameworks (MOFs) are entering many fields, including those mentioned above due to their wide structural diversity, structural flexibility and high tunability. In this work, we investigate the hitherto unexplored effects of forced wetting (intrusion-extrusion) of a hybrid mixed-linker ZIF-7-8 MOF (Zn-methylimidazole 0.794 –benzimidazole 0.206 ) with water. Surprisingly, despite its structural similarity to ZIF-8, the hybrid ZIF-7-8 MOF demonstrates a non-hysteretic water intrusion-extrusion cycle that is in strong contrast to both ZIF-8 and ZIF-7 MOFs, which have pronounced intrusion-extrusion hysteresis. We used a combination of high-pressure intrusion-extrusion experiments, neutron diffraction structural analysis and atomistic simulations to put forward several hypotheses regarding the observed transformation from shock absorber/bumper behavior of ZIF-8 and ZIF-7 to molecular spring behavior of hybrid ZIF-7-8. These results open a new route for tuning the intrusion-extrusion (wetting-dewetting) hysteresis for numerous applications. • First mixed-linker Metal-Organic Framework tested for thermomechanical energy storage via water intrusion-extrusion cycle. • Linker hybridization in ZIF-7-8 shifts from energy absorption to energy storage under hydrostatic pressure. • Benzimidazole linker reduces pore size, volume, and flexibility in ZIF-7-8, confirmed by neutron diffraction measurements. • This raises a nanoscale novel phenomenology for tuning and studying the wettability of nanoporous MOFs particularly for energy applications.