Term for sacrifice that causes opponent to block an escape square? A decoy or deflection typically lure an opponent's piece away from a square. What is it called when you sacrifice in order to lure/force an opponent to a certain square in order to prevent another piece escaping? 

Here is a bad example that I've made that shows the idea. The reason it's bad is because the lure isn't actually needed since d8 is already attacked by the black rook.

[FEN "3r1rk1/ppp2ppp/8/2b5/4P1RP/5q2/PPQ5/RN2KN2 b - - 0 1"]

1... Rd1+ 2. Qxd1 Qf2#
What you are looking for is called "attraction". That is, you attract a piece to a specific square. One of the most famous types of attraction is seen in this example:

 [FEN "r1b2rk1/pp2pp1p/1qp3p1/4Q3/1n1N4/1P6/PBP2PPP/R4RK1 w - - 0 1"]

 1. Qg7+ Kxg7 2. Nf5+ Kg8 3. Nh6#


Here is a nice link with another example.

This is also exactly a deflection since you deflected the queen away from f2. By the way, 1...Bf2 2. Qxf2 Rd1 also the same.

Here are two examples of what Rewan Demontay described as "self-blocking" below. In the first, a study by Nimzovich, it is what I believe the OP is asking for. The other is another type of self-blocking move, but it is not the opponent that forces it. This is more common in some endgame tactics to draw where one side walls the king in so it will be a stalemate.

 [FEN "5rn1/2N1npk1/R7/4P3/8/4P3/Q7/K6R w - - 0 1"]

 1. Rg6+ $3 fxg6 (1... Nxg6 2. Qxf7+ Rxf7 (2... Kxf7 3. Rh7#) 3. Ne6#) 2. Qf7+ $3 Rxf7 (2... Kxf7 3. Rh7#) 3. Ne6#


Here is the other self-block, but for another reason.

 [FEN "8/r6k/3r3p/5p1K/5P2/p6P/Q7/8 w - - 0 0"]

 1. h4 Rd1 2. Qf7+ Rxf7 {Stalemate}