Influence of the surface chemistry of metal-organic polyhedra in their assembly into ultrathin films for gas separation

The formation of ultrathin films of Rh-based porous metal–organic polyhedra (Rh-MOPs) by the Langmuir–Blodgett method has been explored. Homogeneous and dense monolayer films were formed at the air–water interface either using two different coordinatively alkyl-functionalized Rh-MOPs (HRhMOP(diz)12 and HRhMOP(oiz)12) or by in situ incorporation of aliphatic chains to the axial sites of dirhodium paddlewheels of another Rh-MOP (OHRhMOP) at the air–liquid interface. All these Rh-MOP monolayers were successively deposited onto different substrates in order to obtain multilayer films with controllable thicknesses. Aliphatic chains were partially removed from HRhMOP(diz)12 films post-synthetically by a simple acid treatment, resulting in a relevant modification of the film hydrophobicity. Moreover, the CO2/N2 separation performance of Rh-MOP-supported membranes was also evaluated, proving that they can be used as selective layers for efficient CO2 separation.
This work was funded by MCIN/AEI/10.13039/501100011033 and ERDF “A way of making Europe” (grant PID2019-105881RB-I00). The authors also acknowledge the support from the Spanish MINECO (project RTI2018-095622-B-I00) and the Catalan AGAUR (project 2017 SGR 238). It was also funded by the CERCA Programme/Generalitat de Catalunya and through a fellowship (LCF/BQ/PR20/11770011) from “la Caixa” Foundation (ID 100010434). ICN2 is supported by the Severo Ochoa programme from the Spanish MINECO (grant no. SEV-2017-0706). I.T. and M.P.-M. gratefully acknowledge their DGA PhD fellowship from Government of Aragon. The microscopy work was carried out in the Laboratorio de Microscopias Avanzadas at the Instituto de Nanociencia y Materiales de Aragon (LMA-INMA). This work benefited from the use of the SasView application, originally developed under NSF award DMR-0520547. SasView contains code developed with funding from the European Union’s Horizon 2020 research and innovation programme under the SINE2020 project, grant agreement no. 654000. The authors thank the synchrotron SOLEIL for beamtime provision under projects 20190435 and 20191874.