Scaling up multiphase photochemical reactions using translucent monoliths

•Scale-up methodology to design light sources and translucent monoliths.•Successful scale-up of liquid and G/L photoreactions with translucent monoliths.•Slug flow to intensify reactions by alleviating mass transfer limitations and introduce mixing.•Comparison of state-of-the-art and novel translucent monoliths.•High productivity and energy efficiency of monoliths compared to other state-of-the-art designs.