(30e) A Combined Experimental-Simulation Design Approach to Multi-Porous Covalent Organic Frameworks (COFs)

Authors: 
Snyder, M. A., Lehigh University
Das, S., Lehigh University
Maula, T. A., Lehigh University
Mittal, J., Lehigh University
Rangarajan, S., Lehigh University
The ability to synthesize covalent organic frameworks (COFs) with structure and function tailored to specific applications requires a strategy suitable for navigating complexities associated with building block (BB) identification, synthesis, and assembly into target frameworks. In this talk, we will demonstrate a computational-experimental design approach to accomplish this task. The approach employs coarse-grained simulations to identify the geometry and number of orthogonal functionalities of building block ligands suitable for efficient assembly into extended porous crystalline frameworks.1 The resulting coarse-grained models are then translated to detailed molecular representations that match the structural and functional constraints. Synthesis routes to the ligands themselves, as well as conditions for their assembly into extended frameworks, are identified, with characterization of the resulting frameworks providing feedback for upstream model refinement.

In this talk, we will specifically demonstrate this computational-experimental design approach for the direct, bottom-up synthesis of a new tri-porous COF comprised of a combined imine and boronate ester backbone. New structural BBs, with geometry and orthogonal functionalities identified by coarse-grained simulations, have been synthesized and successfully assembled, under ambient to solvothermal conditions, into extended structures. Synthesis-structure relations correlating the extent of crystallinity of the resulting frameworks with solvents and catalysts used for solvothermal synthesis will be presented. Specifically, comparisons will be made between how acetic acid versus Lewis acids (e.g., metal triflate)2 can be exploited to selectively catalyze imine bond formation without affecting borane bond formation. Comprehensive characterization of the structure and stability of these materials will be presented, including insight into the tri-porous framework by a combination of N2, Ar, and CO2 physisorption and X-ray diffraction indexed on the basis of simulated diffraction patterns. Solid-state NMR, FTIR, CHN elemental analysis, and XPS reveal insight into the imine and boronate ester linkages, and SEM and TEM analyses have been used to investigate the morphology and porous architecture. On the basis of this example, the prospects of the computational-experimental design approach for the rational design of application-tailored COFs tailored will be discussed.