The effective sorption capacity of crystalline microporous materials with obstructed internal pore networks is calculated. We present Monte Carlo calculations of the sorption capacity of one-, two-, and three-dimensional networks with defects typical of zeolitic materials. Blockages in the windows and main pores lead to a reduction in sorption capacity. Interconnections between the main pores substantially moderate the reduction relative to that of isolated one-dimensional channels. A significant fraction of the micropore capacity, however, is available only below a percolation threshold in blocking probability. Explicit results for various crystallite sizes are presented.