Potential use of metal organic framework composites by recycling 4-nitrophenol in wastewater for electrocatalytic hydrogen production: A waste-to-profit approach

Development of efficient and sustainable hydrogen evolution reaction (HER) electrocatalyst is crucial for advancing green hydrogen technology. Herein, a waste-to-profit strategy is proposed wherein metal–organic frameworks (Cu-BTC and Cu-BDC) are employed for the removal of 4-nitrophenol (4NP) from wastewater and use the resultant adsorbent–adsorbate composites (Cu-BTC4NP and Cu-BDC4NP) for HER. MOFs were synthesised hydrothermally, and their effective adsorption of 4NP was confirmed through equilibrium and kinetic studies, revealing high adsorption capacities exceeding 500 mg g −1 . Linear sweep voltammetry (LSV) revealed that Cu-BDC required low overpotential of 133.99 mV to reach a current density of 10 mA cm −2 compared to the 4NP-loaded composites which exhibited higher overpotentials of 175.54 mV (Cu-BTC4NP) and 203.88 Mv (Cu-BDC4NP). This decline suggests that 4NP adsorption modifies the electronic environment of Cu active sites and may induce framework instability in aqueous media, where hydrolysis of metal–carboxylate bonds is a concern.