Amorphous porous Fe-BTC prepared via the post-synthetic metal-ion metathesis of HKUST-1

Abstract

“Defect engineering”, in which defects are intentionally introduced into metal-organic frameworks (MOFs) with the aim of functionalizing pores and modifying their size distributions, has recently attracted considerable interest. Unfortunately, the surface area of a MOF is inversely proportional to the number of defects, which is the main drawback associated with defect generation; consequently, amorphous MOFs are not very porous. Herein, we prepared Fe-BTC (BTC = 1,3,5-benzenetricarboxylic acid), a defect-rich, amorphous, but porous material, via the post-synthetic metal-ion metathesis (PSMM) of CuZn-HKUST-1 with Fe2+/Fe3+. Zn2+ is relatively weakly bound to BTC3− and is easily replaced by Fe2+/Fe3+, whereas Cu2+ forms stable bonds that maintain the overall MOF structure during the PSMM. Subsequent oxidation of all Fe states to Fe3+ creates significant defects and disorder at metal nodes. While the resulting amorphous Fe-BTC is of similar porosity to Cu-HKUST-1, defects at its metal sites accelerate reactions involving Lewis acid catalysis. © 2023 The Royal Society of Chemistry.