Sulfur-empowered porous frameworks as sensors, semiconductors and catalysts

The story is one of closing the gaps, i.e., the insulating gap in metal-organic frameworks (MOFs), and the gap in the synthetic strategies for porous metal-thiolate solids; both critically relevant to next-generation electronic and catalytic materials. We recount the quest for recipes—the ones broadly effective for tackling the intractable metal-sulfur link in both network construction and in catalytic applications. In a simple, one-pot recipe, rigid, chelating aromatic thiols directly react with metal ions to form porous frameworks. The resultant metal-dithiolene nets inaugurate a class of covalent metal-organic frameworks (CMOF) that not only feature versatile electroactive and ion-exchange capabilities, but also bridge the two parallel fields of MOFs and porous polymers. In the hard-and-soft design, carboxyl and sulfur groups make for a versatile, stepwise approach: 1) hard ions like Zr(IV) selectively engages the carboxyl groups to set up the host net; 2) the dangling thiol donors can then take up metal guests to afford the metal-thiolate function which can be deployed either as electroactive cross-links for closing up the insulating gap in the solid state framework, or as solitary units with open metal sites for leach-free, bona fide heterogeneous catalysis.