Tunable Metal-Organic Frameworks Based on 8-Connected Metal Trimers for High Ethane Uptake

Metal trimers [M-3(O/OH)](OOCR)(6)are among the most important structural building blocks. From these trimers, a great success has been achieved in the design of 6- or 9-connected framework materials with various topological features and outstanding gas-sorption properties. In comparison, 8-connected trimer-based metal-organic frameworks (MOFs) are rare. Given multiple competitive pathways for the formation of 6- or 9-connected frameworks, it remains challenging to identify synthetic or structural parameters that can be used to direct the self-assembly process toward trimer-based 8-connected materials. Here, a viable strategy called angle bending modulation is revealed for creating a prototypical MOF type based on 8-connected M-3(OH)(OOCR)(5)(Py-R)(3)trimers (M = Zn, Co, Fe). As a proof of concept, six members in this family are synthesized using three types of ligands (CPM-80, -81, and -82). These materials do not possess open-metal sites and show excellent uptake capacity for various hydrocarbon gas molecules and inverse C2H6/C(2)H(4)selectivity. CPM-81-Co, made from 2,5-furandicarboxylate and isonicotinate, features selectivity of 1.80 with high uptake capacity for ethane (123 cm(3)g(-1)) and ethylene (113 cm(3)g(-1)) at 298 K and 1 bar.

Automated summary

A novel metal-organic framework based on 8-connected metal trimers has been successfully created using a strategy called angle bending modulation. These materials show excellent gas-sorption properties, particularly in terms of adsorption capacity and selectivity for various hydrocarbon gas molecules. The study also demonstrates that six members in this family with different gas adsorption performances can be synthesized using different types of ligands.