Ligand Substitution: An Effective Way for Tuning Structures of ZIF-7 Nanoparticles (NPs) and Improving Energy Recovery Performance of ZIF/PA TFN Membranes.

It is an important initiative to reduce the building energy consumption using energy recovering ventilation (ERV) systems. The application of ERV systems is hindered by the low CO 2 barrier performance of commercial total heat exchange membranes (THEMs) that lead to unsatisfactory indoor air refreshing rate, and there is an urgent need for THEMs that have improved CO 2 barrier properties and effective energy recovery efficiencies. Here, we report the formation of novel ZIF/PA TFN THEMs based on ZIF-7-X nanoparticles (NPs) with "core-shell" structures and tunable particle sizes, formed from benzimidazole (BIM) ligands and BIM substituted by -NH 2 , -CH 3 , -C 2 H 5 , and -C 3 H 7 functional groups. The NPs were mixed with pyr omellitic triformyl chloride (TMC) in the organic phase during the interface polymerization process to form ZIF/PA TFN membranes. The total heat exchange performance of ZIF/PA TFN membranes could be effectively modified by the type and quantity of ZIF-7-X NPs added. The CO 2 barrier properties and water vapor permeability of ZIF/PA TFN membranes could be improved by the addition of optimal levels of ZIF-7-X NPs, showing low CO 2 permeance of 7.76 GPU, high H 2 O permeance of 663.8 GPU, and excellent enthalpy exchange efficiency of 72.1%. This work provided an effective strategy for tuning not only the nanostructures of ZIF-7 fillers but also the CO 2 barrier properties of the formed ZIF/PA TFN membranes.