How to achieve unassisted, economical, scalable, and sustainable artificial photosynthesis to liquid fuels/products with high solar-to-fuel efficiency (STFE), to address carbon-neutral economy? An attempt has been made to simulate few critical aspects of green photosynthesis in an artificial leaf device. Apart from broad solar light absorption, critically, extent of charge separation at heterojunctions, and charge utilization decides the STFE. Towards this end, sunlight absorbing BiVO4 quantum dots (BVQDs) is assembled from ionic-precursors into TiO2 pores, and integrated them structurally and electronically. BVQDs in TiO2 pores leads to all-inorganic system with sub-quadrillion heterojunctions in 1 cm2 device (contains ~1 mg TiO2+BiVO4) and facilitates artificial photosynthesis. We demonstrate about 30 % STFE with wireless BiVO4-TiO2 artificial leaf device to HCHO and CH3OH, and address scalability and sustainability. Assuming no change in STFE, 6.74 m2 device is expected to convert 1 kg/h CO2 into C1-oxygenates in sunlight.