One‐Pot Synthesis of Heterobimetallic Metal–Organic Frameworks (MOFs) for Multifunctional Catalysis

Abstract

A one‐pot synthesis of bimetallic metal–organic frameworks (Co/Fe‐MOFs) was achieved by treating stoichiometric amounts of Fe and Co salts with 2‐aminoterephthalic acid (NH 2‐BDC). Monometallic Fe (catalyst A) and Co (catalyst F) were also prepared along with mixed‐metal Fe/Co catalysts (B–E) by changing the Fe/Co ratio. For mixed‐metal catalysts (B–E) SEM energy‐dispersive X‐ray (EDX) analysis confirmed the incorporation of both Fe and Co in the catalysts. However, a spindle‐shaped morphology, typically known for the Fe‐MIL‐88B structure and confirmed by PXRD analysis, was only observed for catalysts A–D. To test the catalytic potential of mixed‐metal MOFs, reduction of nitroarenes was selected as a benchmark reaction. Incorporation of Co enhanced the activity of the catalysts compared with the parent NH 2‐BDC‐Fe catalyst. These MOFs were also tested as electrocatalysts for the oxygen evolution reaction (OER) and the best activity was exhibited by mixed‐metal Fe/Co‐MOF (Fe/Co batch ratio=1). The catalyst provided a current density of 10 mA cm−2 at 410 mV overpotential, which is comparable to the benchmark OER catalyst (i.e., RuO 2). Moreover, it showed long‐term stability in 1 m KOH. In a third catalytic test, dehydrogenation of sodium borohydride showed high activity (turnover frequency=87 min−1) and hydrogen generation rate (67 L min−1 g−1 catalyst). This is the first example of the synthesis of bimetallic MOFs as multifunctional catalysts particularly for catalytic reduction of nitroarenes and dehydrogenation reactions.