Facile Synthesis of Metallosalphen-Based 2D Conductive Metal-Organic Frameworks for NO2 Sensing: Metal Coordination Induced Planarization

As an emerging class of promising porous materials, the development of two-dimensional conductive metal organic frameworks (2D c-MOFs) is hampered by the few categories and tedious synthesis of the specific ligands. Herein, we developed a nonplanar hexahydroxyl-functionalized Salphen ligand (6OH-Salphen) through a facile two-step synthesis, which was further applied to construct layered 2D c-MOFs through in situ one pot synthesis based on the synergistic metal binding effect of the N2O2 pocket of Salphen. Interestingly, the C-2v-symmetry of ligand endows Cu-Salphen-MOF with periodically heterogeneous pore structures. Benefitting from the higher metal density and shorter in-plane metal-metal distance, Cu-Salphen-MOF showcased excellent NO2 sensing performance with good sensitivity, selectivity and reversibility. The current work opens up a new avenue to construct 2D c-MOF directly from nonplanar ligands, which greatly simplifies the synthesis and provides new possibilities for preparing different topological 2D c-MOF based functional materials.

Automated summary

We developed a nonplanar hexahydroxyl-functionalized Salphen ligand (6OH-Salphen) through a facile two-step synthesis and used it to construct layered 2D c-MOFs through in situ one pot synthesis based on the synergistic metal binding effect of the N2O2 pocket of Salphen. The Cu-Salphen-MOF exhibited periodically heterogeneous pore structures due to the C-2v symmetry of the ligand. With higher metal density and shorter in-plane metal-metal distance, Cu-Salphen-MOF showed excellent NO2 sensing performance with good sensitivity, selectivity, and reversibility. This work provides a new approach to directly construct 2D c-MOFs from nonplanar ligands, simplifying the synthesis process and offering new possibilities for preparing functional materials with different topologies.