A series of organosilica sols are prepared by the polymeric sol-gel method using 1, 2-bis(triethoxysilyl)ethane (BTESE) as the precursor. Particle size distributions of the BTESE-derived sols are systematically investigated by carefully adjusting the synthesis parameters (i.e., water ratios, acid ratios and solvent ratios) in the sol process. In certain conditions, increasing the water ratio or the acid ratio tends to cause larger sol sizes and bimodal particle size distributions. However, higher solvent ratios lead to smaller sol sizes and unimodal particle size distributions. The organosilica membranes prepared from the optimized sols show excellent H-2 permeances (up to 4.2 x 10(-7) mol.m(-2).s(-1).Pa-1) and gas permselectitivies (H-2/CO2 is 9.5, H-2/N-2 is 50 and H-2/CH4 is 68). This study offers significant insights into the relationship between the sol synthesis parameters, sol sizes and membrane performance. (C) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.