Efficient recovery of gold using Macroporous Metal-Organic framework prepared by the 'MOF in MOF' method

The design of an efficient adsorbent for Au(III) has remained a challenging research focus, as the adsorbent needs to overcome competition from other ions while simultaneously addressing pore blockage caused by the reduction of Au(III) to elemental gold. In this study, we report the synthesis of a hierarchically porous metal-organic frameworks (MOFs) with ultra-large pores (300 nm) using the "MOF in MOF" method. This material facilitates enhanced adsorption kinetics by increasing the rate of gold ion adsorption and effectively prevents pore blockage resulting from Au(III) reduction, enabling access to the majority of adsorption sites. Batch experiments were conducted, and various complex water mixtures, including freshwater, simulated electronic waste solution, and gold ore leachate, were tested to demonstrate the rapid extraction of trace amounts of gold by the developed adsorbent. Remarkably, without additional functionalization, the adsorbent solely based on its pore advantage achieved a gold adsorption capacity of 1184 mg/g and reached 80 % adsorption within just 5 min (C0 = 100 mg/ L, V/m = 2 L/g). Furthermore, the gold recovered from the leachate of gold ore exhibited a purity of 23.8 K (99.2 % purity).