Energy-efficient removal of trace VOCs from humid air using metal-organic gel derived porous carbon

The development of granular adsorbents for the efficient capture of low-concentration volatile organic compounds (VOCs) from humid air are highly desirable. Herein, we report the synthesis of granular ZIF-8 monolith ( mono ZIF-8) featuring high surface area (2312 m 2 /g) and mesoporous structure by shortening the synthesis time and optimizing the reactant concentrations, which was further carbonized at 1000 °C to obtain porous granular carbon. As-prepared ZIF-8-C1000 exhibited high surface area (1623 m 2 /g), hierarchical porous structure (0.5–10 nm) and hydrophobicity (water contact angle 145.8°), thus it showed very high adsorption performance for trace VOCs like toluene and hexanal under both dry and humid conditions (relative humidity 30 %-80 %) at 25 °C, much higher than commercial activated carbon (AC) such as BPL-AC, coconut shell AC, and representative MOFs including HKUST-1, mono HKUST-1, mono MIL-100(Fe), MIL-101(Cr) and MOF-235. Additionally, ZIF-8-C1000 could be rapidly regenerated under mild temperatures (60 °C to 80 °C), while BPL-AC requires a higher desorption temperature and more time due to disordered porosity. The exceptional adsorption and desorption performance of granular ZIF-8-C1000 over BPL-AC can be attributed to its interconnected micropores and mesopores.