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The primary objective of the present study is to compare the result of adding a microwave-heating pre-step (MW) to the conventional electrical heating method (CE) to synthesize chromium benzenedicarboxylate, MIL-101(Cr), for CO2 adsorption applications. The results show that using conventional CE the time required to complete the synthesis reaction is 24 h while adding a short-period MW to CE as a pre-step can reduce this time to 5 h. The MW pre-step can be carried out under either autogenous pressure or atmospheric condition. The results also revealed that both methods are capable of producing MIL-101(Cr); however, CE method can produce the adsorbent with the CO2 adsorption capacity 7.7 mmol/g at 5.0 bar and 25˚C, while the adsorbent synthesized using hybrid method can possess the adsorption capacity 6.1 mmol/g at the same condition. [ABSTRACT FROM AUTHOR]

MIL-101(Cr) crystals were synthesized through a dual-step procedure consisting of a short term nucleation step in which the solution mixture was heated using microwave irradiation (MW phase) followed by a long-term growth step in which conventional electrical heating (CE phase) was used as a source of energy. The primary objective of such segregation is to increase the nuclei population at the end of the nucleation step. As a result of the high population density of nuclei, it is expected that the total time required to grow crystals in the CE phase decreases. The results showed that using the dual-step procedure led to a significant reduction in total synthesis time. The results also revealed that increasing pH from around 1.5 to 3 at the beginning of the CE phase resulted in producing octahedral crystals instead of a multifaceted sphere. Octahedral crystals exhibit higher CO 2 adsorption capacity than the multifaceted ones. Using the dual step procedure, one can not only control the morphology but also reduce the total synthesis time of MIL-101(Cr) crystals. Image 1 • Synthesis of MIL-101(Cr) crystals with separation of the nucleation and growth steps. • Controlling morphology by using a microwave irradiation and a conventional electrical heating. • Obtaining octahedral and multifaceted sphere shapes with reaction condition control. • Higher CO 2 adsorption capacity with octahedral morphology. [ABSTRACT FROM AUTHOR]