Cu3BTC2 MOF-impregnated boron-doped biochar derived from orange peels for enhanced NH3 capture

Ammonia (NH3) is a typical malodorous pollutant and one of the key factors causing PM2.5. This study proposed a one-pot impregnating method to synthesize a novel NH3 sorbent-boron (B)-doped biochar derived from waste orange peels impregnated with Cu3BTC2 MOFs (i.e., HKUST-1/BBC). Boric acid activation, boron-doping, and HKUST-1 impregnation provided a structure with more pores and sorption sites on the surface of the HKUST-1/BBC composite. The as-fabricated HKUST-1/BBC-5-2.5 (5 representing the mass ratios of added H3BO4 to orange peels powder, 2.5 indicating the mass ratio of B-doped porous biochar BBC-5 to pure HKUST-1) had a 3.71 at.% nitrogen and 1.96 at.% boron content, as well as the largest specific surface area of 674.31 m2·g−1, delivering an outstanding NH3 capture capacity of 10.44 mmol·g−1 at 298 K and 100 kPa, and a fast sorption kinetics (circa 95 % of balance capacity after 15 min), and moderate heat of sorption (25 to 50 kJ·mol−1). The sorption mechanism of NH3 on HKUST-1/BBC-5-2.5 was proposed to be a reactive adsorption process. This study demonstrates the HKUST-1/BBC-5-2.5 as a sorbent for enhanced NH3 capture, as well as offers a facile and scalable production strategy for processing waste peels as adsorbent to absorb waste gas.