The reaction conditions for the synthesis of Cu–BTC (BTC = benzene-1,3,5-tricarboxylic acid) were elucidated using a continuous-flow microreactor-assisted solvothermal system to achieve crystal size and phase control. A high-rate synthesis of Cu–BTC metal–organic frameworks with a BET surface area of more than 1600 m² g⁻¹ (Langmuir surface area of more than 2000 m² g⁻¹) and with a 97% production yield could be achieved with a total reaction time of 5 minutes.

High temperature gas–solid reactions interactions are ubiquitous in and on the Earth and other planetary bodies (Fig. 1). In these natural systems, gases are elusive. Like a hurricane’s wind that leaves a path of destruction but no trace of wind after the event, the gas that initiated a gas–solid reaction may be conspicuously absent. Because gases effectively escape from geologic systems, gas–solid reactions may only be recorded by their stable, or metastable, solid reaction products.

A Na-doped p-type flower-like ZnO photocatalyst (Na:ZnO) that is highly visible-light-sensitive in air at room temperature was synthesized by a continuous flow microreactor, where NaOH was used as both the precipitating and doping agent. The results of various characterization techniques (XPS, ICP, ToF-SIMS, XRD, and HRTEM) indicated that the Na ions have been successfully doped into the ZnO lattice. The Na:ZnO demonstrated a much higher photocatalytic degradation rate of methylene blue under simulated sunlight (λ_max = 494 nm) than the rates obtained from commercially available TiO₂ photocatalysts (P-25) and pure ZnO. This much enhanced rate is likely a result of increased surface defect sites associated with oxygen when Na replaces Zn in the crystal structure. A possible mechanism of the photocatalytic degradation of methylene blue on the Na:ZnO is suggested.