Integrated Monomer Synthesis and Framework Assembly: Achieving Isoreticular Modulation of Hydrogen-Bonded Organic Frameworks

Systematic construction of isoreticular hydrogen-bonded organic frameworks (HOFs) promises tailored material properties crucial for diverse applications, yet is challenging due to the weak, flexible, and non-directional nature of hydrogen bonds. Herein, we develop an "integrated monomer synthesis-framework assembly" (ISA) methodology for constructing a series of isoreticular HOFs. Unlike traditional methods where monomers are first synthesized and then assembled into HOFs, the ISA system employs dicyandiamide rigid hydrogen-bonded hexameric clusters as connecting nodes to covalently react with planarized C3-symmetric cyano-precursors (C3-CPs) to generate diaminotriazine (DAT) monomers, while simultaneously inducing the directional assembly into isoreticular (6,3)-net hcb topological DAT-C6-HOFs. The pore sizes and microenvironments of the resulting DAT-C6-HOFs can be precisely tuned by varying the structural modulation (length and steric hindrance) of the pi-bridge on C3-CPs, enabling highly selective sensing towards perfluorooctanoic acid over other homologous molecules, that are difficult to be separated and detected by chromatography. Overall, the ISA methodology facilitates the scalable creation of families of isostructural HOFs and provides a customized structural platform for investigating factors beyond topology that impact the capturing, releasing, and responding to guest molecules.