Intensification of hydrogen adsorption by novel Cu-BDC@rGO composite material synthesized in a microwave-assisted circular micro-channel.

Graphical abstract Highlights • Intensification of hydrogen adsorption capacity, stability, and production yield for Cu-BDC@rGO composite. • Fast and continuous synthesis of Cu-BDC@rGO composite materials by MW-assisted microfluidic heating for the first time. • Investigating the effect of Cu-BDC@GO shape (worm-like and sandwich-like) or synthesis root on hydrogen adsorption. • Reducing reaction time and reactor size upto few seconds and micrometers for synthesis of MOF-Carbon hybrid materials. • Using RSM experimental design to evaluate the effective parameters. Abstract In this study, pure Cu-BDC and composite Cu-BDC@rGO were produced by combining microwave irradiation and microfluidics (MW-assisted microfluidic) to intensify the hydrogen adsorption. To compare two heating methods, pure Cu-BDC was synthesized by both MW-assisted microfluidic and conventional heating methods. Results showed that the production yield and hydrogen adsorption capacity of Cu-BDC was 18% and 26% greater for MW-assisted microfluidic heating, respectively. In addition to the results, this method brings some advantageous such as lower reaction time, lower reactor size, more uniform crystal shape, and lower crystal size compared to conventional heating. So, the MW-assisted microfluidic method was selected for further investigations. Response surface method (RSM) applied to find the optimum synthesis condition of the material for hydrogen uptake. In this regard, GO content, metal/linker molar ratio, and microwave (MW) time selected as independent, and the hydrogen adsorption at 77 K and 40 bar selected as the dependent response. Also, experiments showed that the one pot synthesis of Cu-BDC@rGO (sandwich-like adsorbent) has the best hydrogen uptake compared to pure Cu-BDC (cubic adsorbent) and the other sample (worm-like adsorbent) which is confirmed the effect of modulating synthesis route. Finally, it must be said that the incorporation of GO and MW-assisted microfluidic heating improved the specific surface area, pore volume, throughput, and thermal stability of the adsorbent. [ABSTRACT FROM AUTHOR]