Electrostatic self-assembly of monolithic MOF-based carbon sponges for the efficient immobilization of gaseous elemental mercury

Synthesized MOF-based carbon sponge materials through electrostatic self-assembly. • The removal efficiency of this material for Hg 0 surpasses traditional limits. • Over 90% removal efficiency for Hg 0 in simulated actual flue gas after 4 cycles. Mercury emissions from coal combustion present persistent risks to both public health and ecosystem integrity. Although powdered adsorbents exhibit high gaseous elemental mercury (Hg 0 ) removal efficiency, their practical deployment is often hindered by particle agglomeration, poor recoverability, and entrainment in flue gas streams. Herein, this article reports a structured monolithic adsorbent CuS-BTC@CMS, fabricated by electrostatic self-assembly of CuS derived from Cu-BTC (BTC = 1,3,5-benzenetricarboxylic acid) onto a carbonized melamine sponge (CMS). Leveraging the spatial confinement effect of the metal organic framework (MOF) precursor, the resulting CuS-BTC demonstrates superior Hg 0 adsorption performance at elevated temperatures (150 °C), achieving an average removal efficiency of 95.91% over 4 h. Mechanistic investigations reveal that polysulfide species (S x 2− ), particularly long-chain variants, serve as the predominant active sites for Hg 0 capture. Through electrostatic interactions, negatively charged CuS-BTC is uniformly assembled onto the positively charged CMS surface, which was pre-functionalized with CTAB (cetyltrimethylammonium bromide), ensuring high dispersion of active components. The macroporous architecture of the support, combined with the well-dispersed CuS-BTC, facilitates efficient Hg 0 transport to reactive sites, enabling CuS-BTC@CMS to achieve an average Hg 0 removal efficiency of 97.4% over 4 h, outperforming the parent Cu-BTC. The monolithic adsorbent maintains excellent Hg 0 removal performance across a wide temperature range (30–180 °C) and exhibits robust tolerance to diverse flue gas components (SO 2 , NO, O 2 CO 2 , and H 2 O), underscoring its adaptability to variable operating conditions. Moreover, it demonstrates favorable regenerability, retaining over 90% Hg 0 removal efficiency after four regeneration cycles. The maximum Hg 0 adsorption capacity of CuS-BTC@CMS reaches 11.87 mg/g with the breakthrough ratio of 99.97%, corresponding to 108.41 mg/g when normalized to the CuS-BTC loading. Download: Download high-res image (116KB) Download: Download full-size image